Edit to add, is this the little boy you spoke of in http://www.mamapedia.com/questions/17225607357262921729?
In THAT case, I think the poor kid is being sent to the wolves. His behavior is because he doesn't have a consistent home or caregiver or set of rules. On the one hand, the consistency of school might be a good thing for him. On the other, he has a lot of problems with his home life and is suffering from the fact that everyone passes him around like a hot potato. I sadly suspect that if he doesn't somehow take to school easily, he will be labeled and still not get the discipline he needs. Expecting the school to reform him is just more passing the buck.
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In general, I do not think that a child who has not been taught how to behave will magically start to behave. That applies to all aspects of the child's life. For example, if you allow your child to run around at home during meals, why be surprised if the child also runs around at a restaurant?
EVEN IF the child behaves in pre-k because the teachers don't allow his behavior (assuming said behavior doesn't get him expelled), that doesn't mean he'll also behave elsewhere with different caregivers.
Further, if the issue is something that is untreated (current research indicates that bad sleep can cause bad behavior in some children - friend's DD was asked to leave a preschool before she had her sleep apnea resolved), then there can be a dramatic difference IF the parents get the underlying issue treated.
There are a lot of variables here. If it were my child, I'd be looking for a cause (be it my parenting or a medical issue) because being so "unruly" that I can't take him out in public is huge problem. Friend's daughter is autistic and non-verbal. They still take her out in limited ways, based on her abilities to handle it. If this child was truly not going anywhere - the store, church, the playground...then something needs to be changed.