I wonder if dividing kids into groups is even necessary.
I'm not the first person to say this, but lecturing is obsolete, and probably has been since the Xerox machine. Online video is just another nail in the coffin. We can do non-interactive information transfer cheaply.
It seems to me that you could get a similar, or better, education just by making materials available and then having in-class homework sessions with occasional individualized attention. Kids can proceed at their own pace relative to different subjects.
Some time synchronization might be necessary to have examinations to prove that you know the material. Otherwise I don't see the need for it.
Dividing children into school classes by birth date is a distinctly bad idea and has never been supported by educational research, but rather is resorted to for administrative convenience.
