Hi Ginseng, like Essbee, I felt the need to get a diagnosis to best help my ds who was at the time (and still is) self harming and being violent towards me. TBH, it was either a case of find out what's wrong with him or he gets thrown out the school. He was eventually diagnosed with Aspergers and ADHD and as I put him on Ritalin, as far as they were concerned, problem solved and he was going to be a good little boy from now on. This is certainly not the case though.
I am happy that I got a diagnosis early on (he was 5) so that I knew what i was dealing with and could read up (and more recently, speak to MNers who know what they're talking about) on the subject.
Last week, my ds cried in the car saying that he was losing all his friends and was there something wrong with him? It was heartbreaking and I would not wish that on any other human being, especially my baby.
The choice is obviously yours, but if he were to be diagnosed, I think that the pros would outweigh the cons - cerainly at school. Also in his new school, he may be labelled as a trouble maker if there is no diagnosis. My son still has that label when it is him who is getting bullied and tries to break up fights because he hates to see anyone getting hurt. (in his teachers opinion, he should leave the situation and get help, not try and solve it himself).
My ds is also charming and an absolute delight and ABSOLUTELY LOVES trains! So, I know exactly what you have to listen to...I know what coupling rods are and all the names and types of trains in Thomas the Tank Engine! I am sure more MNers will have more advice to give but I do understand your frustrations. xx