It may or may not be. If the student does not study properly and did not study properly for its entrance exam too and got admission through reservation only, then there are hugh chances of a SC/ST category student not securing a CGPA of 6 and above in NITs/IITs. Because there is reservation in admission to NITs/IITs but there is no reservation during exams/ assessments in NITs/IITs after the admissions are done.

But if a student study properly and also has knowledge about topics, then it is not hard for him/ her to score a CGPA of even 8 and more.

Hope it helps.