I still consider myself new to this even after being here over a year! There is always something to learn or adjust. I would tell my past self to really trust my instincts and don't let the school downplay my perspective, consider me another parent of a special snowflake. I think this is especially important for that MG/HG kiddo who might fly under the radar, does well in school, doesn't cause a fuss there (just at home, ha), but aches for stimulation and learning, and gets underestimated.
Also I'd say to remember there are may avenues to go down and being stuck on an idea or plan just breeds frustration -- be open to alternatives and accept that different solutions work for different kids at different ages.
