Pre-school challenges

A few months back when our family decided I would take a part-time job I knew changes were bound to happen but what none of us realized were the things we'd be dealing with in pre-school.  The first major thing that happened was our 3 yr. old sweet daughter getting bitten on her birthday of all days by a boy !!  I could have ripped the teachers head off but I bit my tongue and was pleasant but firm with them.  The reason we chose for me to stay home with them for 2 years is so they got a good foundation of right from wrong, manners and most of all they were protected and safe with us.  Now we send her off to the world and that foundation is being shaken by behavior from other kids who may not have that foundation.  In addition to getting bitten, the latest thing was a booger was wiped in her hair and another boy kicked dirt at several of the kids.   Mama bear's feathers again have been ruffled should I stay home again and prevent this?  Really this is pre-school!!!  We looked at several schools and this one was faith based and recommended by a friend.  My husband and I have had so many conversations over do we switch her or just have faith it will get better.  We're going pre-school shopping this week to keep our options open but really I didn't expect to have to worry about these things repeatedly between 3 year olds!  I guess parenting is a series of worries and just when you get comfortable with something it changes….