Like most decisions in education, it's the question of what you want to optimize for, minimum, average, or maximum success. That dictates whether you want to separate smart pupils from average pupils, how big your classes should be, how much memorization you require, how much autonomy teachers should have, and many more aspects. The PISA studies provide really interesting data on this.
If you give teachers no autonomy, you will turn teachers who want to wait or push based on situation to the ones who don't. Or they will simply leave.
Just like with any other job, you either command details or you have people doing own decisions. Cant have both.