hey shailesh 

first tell me whether is he getting stream of his choice after 10 th .if he is getting admissions in any school then this is not necessary to reappear .however if he is not getting admissions anywhere he can reappear . 10th class marksheet is just used as a birth certificate and there is no need of it after 12th .so dont worry however if he want to get good marks then he can surely go for it

best wishes