In some parts of the country, parents are arrested for child abandonment for leaving children unattended (that's the situation outside at the school before the doors are open).

Depending on when you have to leave for your commute, the doors may well be locked. And doors being unlocked does not mean you are allowed to leave your child there without ramifications. Again -- leaving a child in a school building without agreed-upon supervision is still a clear display of negligence.

Anyway, these are not serious solutions.