Triggerfish, if your ds has been expelled then it is the duty of your LEA to provide him with an alternative FULL TIME education and I believe they have a legal duty to provide this within 6 days. Off to Google that for you now.
I hope you are a SAHM because otherwise there may be problems for you because if they educate him at home, you or another responsible adult will have to be there.
They may offer a PRU (pupil referral unit) and if they do RESIST LIKE MAD. If your ds does have Aspergers, he will be put with children who may display behaviour that he may copy and it is not desirable in someone with Aspergers as they will only copy to be like the children they are with.
My heart goes out to you. You will have to be strong here and be prepared to fight your LEA to get the right provision and the right school for your ds.
Does he have a Statement at all? If he does not, then I would seriously suggest that you write to your LEA asking them for an assessment for a statement as soon as possible.
My ds has Aspergers (dx when he was 9). He is now 13 and has been out of school a year and he only gets 8 hours home tuition and that I had to fight for with legal help. He is home because he cannot cope in a mainstream situation.