My 5 year old just started Kindergarten this past August and within 3 weeks of going to school, his teacher mentioned that he is not sitting silently in school, not focusing well, making some weird sounds in class, and very sensitive. He had been going to Montessori from his young age and until that point, we didn't get any behavior concerns from his teachers. But after starting school, I feel like his behavior has changed. He is not listening to us well, he needs a constant reminder on simple things such as brushing his teach Lots of tantrum and constantly picking on his sibling (it's always been that way). He goes to Soccer and this week we noticed him picking on a kid in the field itself and not focusing on the game the whole time. He is no longer the kid we knew a few months ago and we are at a loss on how to parent him. When I search on Google, it sounds a lot like ADHD and I have had a discussion with his teacher and she is it's possible it's ADHD. His ped thinks it's too early to diagnose. However, asked me to reach out to a counselor as when she met him she even noticed he is not focusing well. I remember his 5-year annual checkup and his ped mentioned he was a model child as he listened to her and cooperated very well. He is good with math and other learning (either met or exceeded the expectations) and likes to do home work (most of the time). Is it possible for a kid to change this drastically within a span of few months? No changes in our family life. I'm at a loss and it's on my mind all the time. Please help.