You haven't mentioned the class your son has applied for. Neverthless, in 2019, the cut off for Class 6th for SC Category was 185 and for Class 9th, it was 166. With 157 marks, it is a close call. Having said that cut offs change every year depending on various factors and for 2020, the cut off is expected to be around 160-175. If that is the case, then unfortunately, admission might  be tad difficult for your son.