Whats wrong with him?

Just wondering if anyone has been through similar? My 5 year old (nearly 6) has recently started playing up a lot at school. After a .meeting with the head, his teacher and a support lady they think he has separation anxiety and severe anxiety. But he acting acting out angry every day with shouting, throwing chairs, pulling coats of pegs, and has the attitude of "I don't care " "whatever" "do it then" and it just disrupting the class all the time he keep getting taken out of it. They think some of it is all for attention. We have tried sticker reward charts for good behaviour and listening skills etc at school but he's now ripped that up and I am at the point where I don't know what to do anymore. He's kicked teachers and tells me he gets angry but it's seconds from walking though the door to his class. I can't see anything making him angry that quick. He won't join in with activities and refuses to do any work. We made a calm bottle at weekend to get to help him but it's not done anything.  It's like hitting a brick wall with everything we try. They've recommended for a peadatrition to see him but I'm wondering if it's something else or if he needs some calming type medication because he's getting worse and we have this all at home to. He sleeps a good 10-11 hours every night . By going to bed at 6.30 but is ALLWAYS up from 4.30 EVERY morning !!! I'm just at my wots end. What is wrong with him and why is he acting out this way... x