Behaviour after starting preschool

[Poppedcorn]

DS1 is 2yrs 9mths and started preschool last week, for two mornings a week. He seems to be enjoying it and there are no tears when I leave him (even though he's not entirely thrilled about being left). But his behaviour at home has just become horrendous - he's normally pretty chilled out but has turned into a nightmare. This afternoon we've had throwing toys across the room, continually hurting DS2, slamming doors and cheekiness/defiance. It just isn't him.
He outgrew his nap a few months ago but I made him sleep today just in case it was tiredness making him go bonkers, but clearly not.
Is this normal behaviour reacting to a change like this? I'm wondering if he wasn't actually ready for preschool and this is his way of telling me?!

Anyone??

Could easily be starting pre-school that's set him off. Did he attend any kind of nursery previously? Is he used to being apart from you?
If he's used to being with you all day and then he's now got to be with strangers suddenly he might feel a bit unwilling to cooperate and acting like you describe out of anger at you. Bit of a cliche but sounds like he's working out his boundaries in this new situation.

I think giving him time to settle in and form relationships with teachers/other children is needed. You say he goes in fine if a bit indifferent.
He's maybe just getting used to it. You could ask his teacher how he's settling in? How he behaves there? Is he copying another child's behaviour there?

The bad behaviour at home has to stop incase he really hurts DS2. Have you tried time-outs? Must be difficult with DS2 to look after too.