Dear aspirant ,

For joining in IITs , NITs and IIITs through JOSAA counseling you need to score more than 75% in 12th board for CBSC and ISC boards. As you are from ISC board you need to score 75 percent in 12th to get admitted in any of these institutes. Apart from them, if you want to join any engineering college that comes under state government or any other private college you don't have to score such percentage.

But your score in 12th board will not effect your credibility to get any seat in NITs and IITs. Only JEE mains and JEE advance marks are responsible for that.

Hope this helps!