Mainstream school

Hi, My son is 6, he has been diagnosed with ODD and there are further assessments to see if he is ASD, though the believe is PDD.  I'm really worried about his education.  He really can not cope with mainstream school.  He has been on a part time programme, where recently I have had to be his one to one, as his one resigned.  We are being given some respite in that he will be attending a behaviour unit until christmas (he was a pupil there previously and was defiantely more settled).  My worry is that come January, when he has to return to mainstream his behaviour deteoriates again, because he is unable to cope. I have already been told, if his diagnosis is PDD he will have to stay in mainstream.  We are only at the beginning of the statement process.  Any ideas of where I can get some advice, I would be really grateful

Thanks x