We didn't do the OT testing until this year. My daughter started having difficulty in 2nd grade with writing. I fought with her school for about a year over doing an evaluation and eventually broke down and had an outside evaluation done. Her OT evaluation found a 3 year manual dexterity delay and significant muscle weakness in her hands. That is why I would ere on the side of caution. Waiting will just compound any existing delays. Trust yourself. If you feel like something is wrong, don't wait on his school!