In mid-grade school I had a particularly exceptional and progressive teacher who ran experiments like this (Canada)...
Rather than the regular curriculum delivery, each student had a filing box where the entire year's assignments where defined on cards (with references to what pages in what textbooks should be read). The students were allowed to do them as quickly they wished. Once an assignment was completed the card (and the results) were placed back in the box for the teacher to review, grade, and comment on (if needed).
There were almost no "lectures" (read: the teacher standing in front of the classroom talking to the utter boredom of most of the students). In fact, the classroom was broken up into various different areas with partitions upon which the students could stick things -- drawings, notes, etc. There wasn't even line-of-sight from most of the classroom to the blackboard!
Instead, each morning there was a "class meeting" in a common area (with a blackboard) where everyone got to share where they were in their "program", and ask questions or make comments (if they were comfortable doing so). Once a week each student would have a one-on-one "meeting" with the teacher to review progress.
Any student could request additional meetings with the teacher at any time if they were having difficulty with a subject. Often the teacher would then ask a stronger student in a subject to help a weaker student. I was often asked to help in (simple) Maths and (simple) Science. I was often helped in just about all other subjects, like English, Social Studies, etc...
It is interesting how memory works... I had largely forgotten about this exceptional learning environment and experience until this article jogged my memory.
I must try to thank the teacher. He was clearly ahead of his time....