Many schools don't communicate much with parents outside of parent-teacher conferences. The good ones have teachers do some sort of brief written update every week or two for the whole class.
But I also know that teachers don't have a lot of time to field emails from every parent. I only email teachers if I have a time-sensitive or critical issue. For an early dismissal, I'd send a note with the child that morning, but in reality, they don't need advance warning of this -- you just show up at the office and retrieve the child.