Hello Sourav,
You did not mention which of these sibjects was your sixth subject. Considering the best five subjects of yours,  I think that they are Maths 88, Physics 70, Chemistry 63, English 83 and Bengali 90 as your score in Biology is least and for admission in NITs or IITs, having Physics, Chemistry and Mathematics is a must. Well,  your score of best five subjects is 394/500. Your score must be in top 20 percentile of ISC boards in order to get admission in NITs and IITs. As of now, the top 20 percentile of ISC boards is not officially announced yet so it is difficult to predict that. But for an idea,  you can have a look at previous years' top 20 percentile of ISC boards. In 2018, top 20 percentile cutoff was 438/500. In 2017, top 20 percentile cutoff was 427/500 and in 2016, top 20 percentile was 443/500.
I wish you all the best. For any further queries, ask me in the comments.

NIT Kolkata

Admissions Courses & Fees Cutoff Placements Reviews

Shortlist

Brochure