hi,

see cbse board is centralized and its syllabus is followed in many nation wide entrance test like jee main, neet, law entrances,icar etc. your son is in lower classes right now, so thats why you may link that cbse is harder for him, but being in cbse boad has its beneficial when he will be in 10th or 12th level or may preparing for ntse like scholarship exam. however if he admits in other state board, follow the books suggested by teachers in school for any particular domain. also you may take him to coaching institute.