My son had similar issues, we tried everything during the school year. We have extremely helpful teachers, staff, administration, the best group of people I could've asked for. Nothing helped get him on track for longer than a few hours. He was also suspended multiple times his kindergarten year. Eventually we had him diagnosed with ADHD.
He was put on a light dose of Focalin, 10mg. The difference was absolute night and day. There are no major side effects, but he's able to participate and listen to his teachers, he's no longer getting in trouble and has turned around from being one of the more misbehaving children to one who is lead of his class. The difference between his kindergarten year and his first grade year is astounding, and while maturity has some to do with it, his focus is also greatly improved.
I was initially opposed to medication as well, but my son is so much happier now that he's no longer getting in trouble at school, that he's able to sit down and do his work, that he can excel with his class and participate.
If that's the route you end up taking, be candid and open with your doctor about all of your concerns, any questions you may have, everything.