the problem seems to be the difference between the oldest and the youngest kid in a class. OP had problems through his school life as they were always the youngest. so starting the same process a year later doesn't seem to help.

what would help is an adaption of the montessori model where an age range of three years is in a class, and the expectation of all kids behaving the same naturally disappears.

doing that at least in kindergarten will at least avoid a mistaken diagnosis for ADHD. but my hope is that montessori kids will also fare better in a regular school because they learned to be more independent.