Hi S.,
I work in a school special education department as a speech language pathologist. I highly recommend that you first contact your school's special educator director or an administrator to discuss your concerns if you haven't already done so or if you are in a larger school district, you should be contacting someone at the district level.
I would assume that your son's IEP is not being implemented correctly, which is in violation of the law. In our school district, we actually will not suspend a student who is verified in special education.
The purpose of the IEP is simply to outline his needs, where he is at currently and what each staff member wants him to be working on based on his needs and current level of performance. The IEP should not be that difficult to understand if written appropriately. It should state clearly, the goals that each sped staff member has for your son (educational goals, speech/language goals, social goals, behavior goals, etc) The IEP should state who is responsible for implementing each goal and the time and location of when the services should be provided. I am assuming that he is receiving services from a variety of specialists including the SLP, a BD teacher and possibly even OT/PT if he has sensory issues in addition to the special education teacher. Each state is different, but our state has implemented a state wide web site that most districts use (I think only the largest school district in our state uses something else). The IEP might appear to be overwhelming because there is a lot of information, but the main components of the IEP should be easy to understand and should have been explained to you.
There should also be a clearly defined area that discusses how your son's behavior may be impacting his academic success with a clear protocol for procedures to be followed when he is demonstrating inappropriate behavior.
The staff members working with him need to design some sort of system for him to use so that he can identify when he knows that his behavior is escalating so that he can deescalate rather than 'blow' and then demonstrate the behaviors which are getting him in trouble. We have used many systems in our school which allow a student to simply show a card or flag or symbol to let the adults know that his behavior is escalating and the student is allowed to leave the room, no questions asked (of course, a plan is set in advance that if they leave the room they go to a designated area...they can't just roam freely). Does his school have such systems in place?
There are many great books out there for support. I highly suggest that you search some of them out...and share them with your school. Are there any other asperger students in his school? Unfortunately, it sounds as if you are going to have to be a strong advocate for your son...and even more unfortunate, teach the staff.
As a last resort, I would consider contacting your state department of education to express your concerns if you truly feel that you have tried every avenue at your school. I would assume that your state has a set of special education rules and guidelines and that you have received a copy of your parental rights from your school district. Your state department of education may be able to provide some mediation or even help to develop a new IEP together.
Good luck....I hope that your son will get the education that he deserves.