Hi
Please check your education map when school hours are over. If you find houses with no kids or students at all, you have encountered a known bug of disappearing students. I have been closely observing this particular bug and have determined a possible cause – changing or demolishing school bus stops when school buses are picking up/dropping off students. Apparently school buses will be confused by this and leave the city with students in it.
Unfortunately there is no way to reverse this bug. It is best to be cautious in the future when rearranging school bus stops. I suggest one should rearrange when one is certain every students are at home.
Hope this helps.