I'm not primarily talking about math. The same thing holds true across multiple subject areas: by sixth or seventh grade, I was observing extreme differences in academic achievement among students, to the point where it appeared that a non-streamed environment couldn't adequately educate them all together, and the existing non-streamed environment certainly wasn't succeeding at doing so. (To be fair, "all together" included both gifted and low-end special ed students, since everyone was integrated for non-"core" subjects, which unfortunately included French and science.)