My DS15 has Asperger's and we've been through all of the same issues. We found that an interested and understanding teacher was key to our son's success. When he was ready to switch teachers, we would discuss it at his IEP meeting and decide which one we thought would be best for him. In our school, elementary kids would have the same teacher for 2 years so he didn't have to have a brand new teacher every year. I would ask the teacher for a conference at the beginning of the year to discuss my son's issues and how he works best. I would keep an open dialogue with the teacher and pop in most days at pick-up time so the teacher could tell me about any major issues.
One thing that was really important was having printed instructions for each and every assignment. If the teacher verbally told the class to write a paragraph on the moon that was due tomorrow, my son would not write it down or he would get the details or due date wrong. His teachers knew to give him a written assignment sheet, even if it was just quickly hand-written. That was the only way he would get the correct assignment. I helped my son work out a system in his binder to put assignment sheets in one pocket and completed homework in another pocket. We clearly labeled the pockets to make it easier for him. If he didn't turn in an assignment, the teacher would remind him to check his homework pocket.
We also put in his IEP that he's allowed to type assignments in class and for homework. Writing is so hard for him and he'll often write a lot less if he has to do it by hand. When the teacher would let him use the computer, other kids would complain at first but they eventually accepted that he needed to use it.
At the suggestion of our psychologist, we set up a non-verbal system for teachers to use in class with our son. I printed and laminated a set of 3x5 cards with various warnings, reminders or praise. If my son was blurting things out when it wasn't his turn to talk, the teacher would drop a card on his desk with a reminder not to blurt. If my son was distracted and not doing his work, he would get a card reminding him to get back to work. If he quickly turned the behavior around, he would get a card congratulating him on pulling it together. This system saved the teacher from frequently having to stop and talk to my son and saved my son the embarassment of being singled-out all the time.
Having teachers who were willing to make adjustments for our son helped him to do relatively well in 2nd, 3rd, 4th and 5th grade. When he started middle school, things changed a lot. We still had the IEP in place but our son suddenly had multiple teachers, each with different routines and rules. There were 35 kids per class and our son couldn't get the kind of attention he needed to be successful. The school district didn't have an appropriate special ed class for him so we lobbied for a placement in a private school with an Asperger's program. He just finished 8th grade at the school and will be starting his 9th grade year there in a few weeks. We will be looking at Aperger's programs in the high school district over the new few months and then slowly transitioning him back to public school. We're pretty sure he won't make it in a regular mainstream program just yet so we'll keep the special ed component for now.
Hope this helps give you some ideas for your son!