I think it's extremely normal that a 4yo is not ready for the discipline required for grade 1. And most 6yos don't necessarily behave well everyday either. Really can't see why this alone merits a test for ADHD.
In terms of them telling you not to teach him anymore, I think it's hard for other to know how to take this advice. If you have been teaching him because you want to, I'd say it's probably indeed a good idea to stop teaching him what he will learn at school, and focus on things that schools don't cover. If, however, it's the child who really wants to be taught, I would not stop teaching him.
