Kids are asked to solve math tasks in groups and talk a lot. Really? How has it worked in K8, that is, the idea of mixing high achieving kids in math with low achieving kids in the same math class (inclusion) with plenty of group work? I am not sure how students can solve math problems without knowing the necessary math content and skills.
[1] Reference: Stephen Sawchuck in Education Week
Tom Loveless ("High Achievers, Tracking, and Common Core," Brookings report, 2015) describes the effect of detracking math in middle schools such as in the San MateoFoster City School District. He writes, "The changes were brought about by the Common Core State Standards (CCSS). Under previous policies, most eighth graders in the district took Algebra I. Some very sharp math students, who had already completed Algebra I in seventh grade, took Geometry in eighth grade. The new CCSSaligned math program will reduce eighthgrade enrollments in Algebra I and eliminate Geometry altogether as a middle school course." In 2018, many school districts no longer offer Algebra1 in 8th grade. State standards based on Common Core push Algebra I to high school. The detracking move from Algebra I in middle school is contrary to the recommendation by the National Mathematics Advisory Panel (2008) that advocated more students should take Algebra I in middle school, not fewer. Schools (K7) must upgrade the math curriculum to prepare more students for Algebra I in 8th grade. In California, Common Core was a downgrade.
For decades, the detracking in elementary school, for example, has been a recipe for mediocrity. Lackluster achievement climbs up the grades. Thomas Sowell writes, "Equalizing downward by lowering those at the top is a crazy ideaa fallacy of fairnesstaught in the schools of education."
Phil Daro, one of the architects of the detrack plan in San Francisco, writes, "Tracking is an evil." Really? What is evil is equalizing downward. The liberal ideology that students are the same and, therefore, should get the same instruction in math is folly. Moreover, achievement is not privilege. Achievement is achievement. Branding it as privilege subtracts from the hard work, effort, accomplishment, and success of children, including children of color. Contrary to the liberal detracking ideology, "Academic talent, like musical or athletic ability, needs to be assessed, developed, and cheered onward." (Center for Talented Youth, Johns Hopkins)
If you want to know why our children are not learning much, then look into the classrooms of the 21stcentury. Tech has replaced knowledge as the holy grail. The state test has warped and fragmented the curriculum. Not good!
Evgeny Morozov (To Save Everything, Click Here) writes about the folly of technological solutionism. He also points out, "Schools concentrate all their efforts on improving test scores [metrics], even if children learn much less as a result."
Many teachers aren't teaching the right arithmetic, which should focus on the memorization of singledigit number facts that support the standard algorithms. Moreover, they use an inferior curriculum and inefficient methods of instruction. Common Core and its state rebrands are below worldclass benchmarks.
Moreover, our best students are not challenged and underachieve. Kids who are advanced need advanced material. The typical talented and gifted programs found in many school districts don't identify these kids, but the Johns Hopkins Center for Talented Youth (CTY) does that for students in grades 2 to 8 by using the School and College Ability Test or SCAT that is above the student's grade level. It is the only way to sort the most advanced performers (verbal and math) from the rest of the good students that cluster at the top in gradelevel standardized tests. In math, talented youth need textbooks that are written explicitly by math geeks, such as books from the Art of Problem Solving. Beginning in early elementary school, advanced math kids need an entirely different math curriculum taught by an algebra teacher. A recent report from Johns Hopkins shows a widespread lack of support for highability, lowincome students. CTY starts with the Talent Search (SCAT). "Academic talent, like musical or athletic ability, needs to be assessed, developed, and cheered onward."
NAEP National Test 20072017 4thGrade Math Scores Are Flat 
The proficiency standards of the National Assessment of Educational Progress (2017 NAEP)the Nation's Report Cardshow what students “should know and be able to do.” To me, if 60% of the 4th graders, 66% of 8th graders, and 75% of 12th graders can't do math well (not proficient or above), then we have a major problem. Indeed, flat scores in math and reading have been a difficulty in American education for years. Even though many changes have been attempted, they have done little to alter the lackluster NAEP scores. Also, Michael J. Petrilli says the NAEP 2017 indicates a "lost decade of educational progress." In addition to inadequate teaching, the NAEP test scores show that state math standards and curriculum are not world class. Indeed, we teach math poorly. (Incidentally, both math and reading NAEP scores are stagnated.)
Improving State Test Scores is the primary focus of education today.
Political issues seem to dominate the education landscape, but little is said about teaching, itself. Good teaching and plenty of practice are absent in many classrooms. Kids are not learning much because the fundamentals are not taught for mastery. It seems simple enough, but what should teachers do when they are required to follow a reform math curriculum based on CommonCorelaced state standards? The standards are not world class. Reform math is not standard arithmetic. It is an alternative arithmetic and does not emphasize content mastery. Unfortunately, many teachers and schools are judged on their students' test scores.
Teaching is no longer about teaching valued content; it's about improving state test scores (metrics), which is a mistake. "It is difficult to make largescale improvements in education," explains Andrew Ho, a Harvard University professor. For decades, huge reforms haven't worked. The crux of the matter is that teachers aren't teaching straightforward core arithmetic. (And by core, I do not mean Common Core.) Our education system needs international benchmarks of excellence and knowledgeable teachers who can adhere to and teach those standards. We don't have that today. "By international standards, our 8thgrade students are exposed to 6thgrade content" (SchmidtCoganMcKnight).
(Note: Improving state math scores has had little effect on national and international scores. Proficiency on state tests does not correlate well to NAEP. It seems that standardsbased accountability (e.g., Common Core) has led to controversial reforms that don't work well. Learning is flat. For example, test prep for state tests has not impacted NAEP scores. Kids should be taught the fundamentals of standard arithmetic for mastery. They are not. Instead of standard arithmetic, kids are taught reform math, which has had little effect on achievement as measured by the NAEP.)
Algebra
According to mathematician Steven Strogatz, all the symbols, definitions, and procedures of algebra boil down to two activities: solving for x and working with formulae. Young children need to "think about numbers and the
relationships between numbers" Moreover, the "relationships are harder because they much more abstract than numbers," but "they are also much more powerful."
The formula I taught 1st graders for the perimeter of a simple rectangle is P = L + L + W + W (e.g., P = 5 + 5 + 2 + 2 = 14 cm). It made sense that perimeter is a sum of the distances around the rectangle. "To understand mathematics means to be able to do mathematics" (G. Polya). In short, if you can't calculate perimeters (doing the math), then you don't understand perimeters (math).
Strogatz writes (The Joy of x), "Numbers and all mathematical ideas have lives of their own. They obey certain laws and have certain properties, personalities, and ways of combining with one another, and there's nothing we can do about it except watch and try to understand."
1877 
Very young children can learn much more math content than teachers were prepared to teach. It's about learning prerequisites. U.S. students were taught basic arithmetic at earlier ages in the 19th century. Kids in the 1800s learned much more fundamental arithmetic than students learn today, according to Ray's New Intellectual Arithmetic book 1877.
3rd4th Grade Traditional Arithmetic
(Ray's New Intellectual Arithmetic, 1877)
(1) 3/4 of 24 are 6 more than 2/3 of what number?
(2) Find the interest on $50 for 6 months, at 6%.
Progressive educators of the 20th century followed Piaget, which was a significant blunder in American education. Educators should have followed Bruner, who wrote, "We begin with the hypothesis that any subject can be taught effectively in some intellectually honest form to any child at any stage of development."
Thus, we have substantially underestimated what children can learn by saying some content is developmentally inappropriate, which is nonsense. Also, we hide behind the fallacies of learning styles, fairness, averages, and other misconceptions that disregard the cognitive science of learning.
Learning algebra in elementary school started in the 1950s with the Madison Project for grades 3 to 5. I wrote my own algebra curriculum for grades 1 to 3 and added 4th and 5th grade later. In my "early algebra" project (Teach Kids Algebra  TKA), which I started in the spring of 2011 for grades 1 to 3, I contradicted Piaget's theory of cognition every time I gave an algebra lesson, starting with two firstgrade classes, two secondgrade classes, and one thirdgrade class.
1stGrade TKA Student  Spring 2011. 
Very young children can deal with abstractions and do simple reasoning. Numbers, operations, axioms (e.g., a + b = b + a), and equations (e.g., y = x + x + 2) are all abstractions. Writing symbols on paper makes math visual. To learn math, children need to learn symbolics.
The Number Line is important mathematics! It starts at ZERO. Unfortunately, it is seldom used in 1stgrade reform math. 
Number Line showing 3 + 4 = 7 
First Grade: The Standard Algorithm 
The four wholenumber operations should be taught by the 3rd grade. It rarely happens in our schools because the curriculum focuses on reform math, not the mastery of basic arithmetic.
In math, the learning goal should be the mastery of fundamental content (factual and efficient procedural knowledge) in longterm memory, not proficiency on state tests or cumbersome, unorthodox algorithms. Also, a curriculum that is warped to fit test items is a fragmented curriculum that perpetuates lackluster achievement. Common Core and state standards based on Common Core are not world class.
Kids are novices, not experts or pintsized mathematicians. They must master standard arithmetic to advance, but many do not. Kids are stuck in reform math programs that don't work. Knowledge matters in longterm memory. Kids are novices who need to memorize singledigit facts, learn rules and formulae, recognize problem types, and master the mechanics of basic operations to perform standard arithmetic and solve problems.
You can't teach arithmetic like you teach social studies. But, isn't this what most teachers do? Group work! Group work! Group work! Kids aren't going to discover critical mathematical ideas that took geniuses like Euclid, Gauss, Euler, Newton, and many others to figure out.
The primary cognitive building block is knowledge and the skills that are embedded in knowledge. It is factual and procedural knowledge. "Knowledge is critical to thought," says Daniel Willingham, a cognitive scientist.
Knowledge is the foundation that enables a higher level of skills.
Knowledge is critical to thought (Daniel Willingham).
Many schools emphasize higherlevel thinking skills, but not the content knowledge that enables higherlevel thinking. Higherlevel thinking is domain specific. Problemsolving or critical thinking (thought) that is independent of content is empty. Kids who are advanced need advanced content, but they rarely receive it in elementary or middle school. Richard Rusczyk (the Art of Problem Solving), high school calculus is for average students who are prepared. It is too easy for gifted kids in math. The advanced math kids in elementary and middle school should be sorted for math class and taught by an algebraprecalculus teacher. Furthermore, the advanced kids should compete in various math contests (e.g., math league, MathCounts, etc.). Rusczyk's textbooks were written specifically for advanced math kids starting with prealgebra.
Children are easily distracted with gadgets.
They need to focus when they do homework, or little gets done. (And little is learned.)

Students facing each other in small groups of 3 or 4 or at tables are conditioned not to pay attention. Still, paying attention in class is critical for learning. Any interruption or distraction in the classroom [or at home] and there are many, diminishes the working memory and restricts learning. Students must pay attention in class to start the learning process.
Learning arithmetic is hard work. Learning is remembering. If you can't remember something, then you haven't learned it. Learning requires regular practice and frequent review. Forgetting is easy; learning is hard. Thus, learning is hard work, and it is not always fun. If you don't have instant recall of 4 x 8 = 32 from longterm memory, then you haven't learned the fact, and more practice is needed to develop the skill. Indeed, much is taught, but little is learned.
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©2018 LT/ThinkAlgebra