Hlw Sir,
Since your son is in 7th class only and is scoring enough well, guide him about the importance of good marks and improve his studying capacity by guiding him about the imp. Of reading books. Reading books will let him getting the concepts well (help him in doing so too).
Practice is everything, so always ask him to do regular practice of maths like subjects.
Hardwork and practice are everything.
Let him to keep a distance from smartphones.

Teach him everything in a friendly way, as students are very rebellious in nature at this age. Habits inculcated at this age in students are lifelong.
Hope it helps!

Hello Sparsh,

It is not a bad percentage to score,  70-80 percentage,although it is good score enough.He can only work according to his ability,You can only guide him about how to study. But it only depends on him, that how he is getting the things and working on his studies whether he is studying in any board,he can score good score if you want,he have to work with focus and concentration on his study, also if proper guidance will provide to him.