G.M.
Ask about security and what do they do in order to keep the kids safe. Ask about the schools 'gates' and if they keep them closed during school hours in order to keep from kids escaping into dangerous streets. How many teachers are watching the children at playtime outside. During field trips, what is their policy and how many teachers to students do they use. Ratio that is. Ask what their policy is on bullying/aggressive behavior and what they do about it. My son goes to a Charter School here in AZ and they have a 'no tolerance' on bullying and aggressive behavior/violence. Even preschoolers can be little tyrants. My son is in kindergarten and there is a student that went there, that got kicked out because the parents wouldn't work with them on his behavior and he was hitting other kids and wouldn't stop.
Ask about snacks and what they provide for nutrition.
I hope this helps. :-)