my baby was very smart before but After taking admission in school, he is behaving like a dumb person why???

A. Now how are your child is mad that you have to understand for how is your child learnt all these things from and how the school people are teaching them there are two different perspective to look at a situation these parents teach everything with a medium of the screen and everything but when the child goes to the universe is totally different so sometimes the child can take time to pick up the situation