Historical routines are hard to compare against - because they weren't a day/night cycle like we have now. [0]

A lot of kids may have been asleep at noon, like the Spanish siesta, equally, kids may have been involved in the midnight harvest, or caring for the fire.

Things tended towards more of several smaller sleeping periods spread out over the entire day, and periods of activity at times that might feel strange now.

[0] https://www.bbc.com/news/magazine-16964783

Yeah, nail on the head here. I'm pretty sure school schedules are more of an inheritance from the old world than they are a plan to free up parents for more labor. In the old world, school had to be fitted around a kid's work day, not their parents.

Is the 10K years or so that we have been farming enough to change our prior patterns of need?

Even that change isn't as great as we have with clocks and electric light. You don't often need to farm when it's dark out.

Maybe they helped at night when their parents were sleeping?

No, they were expected to wake up soon along with everybody.