I only have a BA in Psychology and don't know what statistics or professionals say but I feel that I learned more in my elementary years than in a four year college! I don't know if it's because I re-entered school to earn my BA late in life and it seemed it was all such a "rush" but it didn't allow me to absorb much of the information!
Have you seen Little House on the Prairie? Did you notice all grade levels were in the same classroom? Well, that's how my early childhood development years in education were; all levels in the same classroom through the eighth grade! "Repetitiveness" is the Key!
Of course, it was a time of segregation and Blacks didn't have money for "After/Before School Care" therefore, the teacher taught us from 7AM to 5PM which allowed time for our parents to work! We were in a small rural community (Population approximately 300) therefore the class consisted of approximately 20-25 children! The (one) teacher had total control! It was nothing to receive lashes on legs with a belt for disobedience with 'no repercussions!'
We were aligned in the classroom by grade level with first graders being on the front row and eighth graders in back. Because of discipline, you could hear a pin fall when the teacher was teaching another grade level. Consequently, first graders were exposed to eighth grade material which created redundancy for all grade levels and smarter children!
PTA was once a month which was very exciting for me because each grade level had competition in math by teacher giving math problem to opponents on blackboard and whoever arrived at the answer first within that grade level would win! Spelling bees the same!
There were no laws preventing entry into elementary school and a child could test as young as five to enter first grade! Today, children should be allowed testing for entry at the age of three because they are much more advanced than we were! I was blessed in that I have an older sister who began teaching me at the age of three and by the time I was four, I could read; therefore, at age five, I was allowed to enter first grade!
We always began our day with the National Anthem, Pledge of Allegiance, and prayer! Discipline was enforced but the "Key" to our success was "Repetitiveness!"
There were no "slow Johnnies" because the teacher worked with each child (as others remained quite) until the child was on level. It was a "true" "No Child Left Behind" setting!