No need to worry so much. The school will be very forgiven. My experiences were:
-- Not writing all items in handbook.
-- Forget to hand in homework
-- Lost the pencil case in school
Anyway, the kids learn very fast and they will follow other classmates. After a few months you will observe your son will become very independent.
For P1, Tak Sun doesn't punish the kids, instead they just write a reminder on the handbook saying "Didn't hand in XXX".
Starting from P2, the school will mark on the handbook everytime if mis-handing in the homework. Accumulating 5 times will receive a warning. If the situation still has no improvement, he will be 記缺点.