You mean doing it as soon as they've aged up to child, without having had their first day of class yet? That's weird if so.
On the one hand, I'm annoyed by their old homework being stuck in their inventories after they age. On the other, I'm thrilled that they do it without being told now! I hated that in Sims 2. Every evening was a herculean struggle. Like in RL, I guess. :-)