Hi Exhausted -
Dealing with the school when you have a 2E child can be exhausting (and frustrating among other emotions!) As others have suggested, medication can be an important step in helping your child. But, this is a personal family decision and having been in your shoes, I can understand your concerns. No teacher has the right or the credentials (unless they are an MD) to diagnose ADHD and prescribe medication. I am glad that you have kept an open mind and considered all options. ADHD is a medical condition that can be treated many ways. Medication is usually the intervention that has the most positive and immediate outcome. But, as you know there are side effects and other considerations. It took me and my husband over two years to allow my son to try. In retrospect, I wish I had not waited as long. You will have to decide when the side effects outweigh the advantages.
OK - then there is the legal issue. It is against the law to mandate medication in the US. I would ask to see the school's written policy on this issue. If you want me to dig up some legal info on this issue, let me know and I will dig it up and post it for you. But, believe me, schools cannot do this. Period.
You mention that your son has reading and writing struggles. Were these areas tested? What were the findings. LD's and ADHD have a high comorbidity rate. If he has a reading disability, it must be treated along with the ADHD. Believe me, stimulants will not teach him the reading skills!!
It is very possible to have adhd and dyslexia and be very very bright. But, without the appropriate support and instruction, the brightness can be lost. Be sure to press the school about all of these issues.
Oh - slow processing speed can be a red flag for ADHD but it does not necessarily confirm the presence of ADHD. Most kids with ADHD and or language based learning disabilities have slower processing and or Working memory compared to their thinking skills (VCI and PRI). But, this is not a hard and fast rule - just a general rule.