(My comment sonly apply to standardized education, not to streaming students into different programs such as specialprograms for gifted students.)
So I guess my points are:
1. I'm doubtful that the "paint by numbers" approach is what the young Picasso needs.
2. Maybe I'm wrong about (1), but we certainly shouldn't subject the advanced students to this method until higher end performance has been measured.
3. I find the attitude of the author, who used the phrase "even things out" as if it was a good thing, concerning. Evening things out should be an explicit non-goal of education.
Some advanced students might even get even better and increase the variance! I can't comment on this program, I know nothing about tutoring. But I know that I personally like breaking things down into little steps, and I think I would have enjoyed a program running on these lines if I was allowed to move at my own pace.
Consider Round 2, where sigma=1.2%, mu=98%. Suppose hypothetically that 90% of students are clustered below 100 (an absolute measure of performance), 96.8% of students are below 150 pts, and 99.2% of students are below 300 pts.
In this case, the absolute variation is huge (300 vs 150). But because only 2.4% of students score between 150 and 300 pts, on a percentile graph, it looks like sigma has been reduced.
I think it's unlikely that this has occurred, but the graphs given don't preclude it.
Furthermore, where do you read that the objective is "low variance"? I read "higher average".
Perhaps one side-effect of the overall improvement is that the teacher doesn't have to spend as much time with struggling students and can devote more time helping high end students unlock their potential.