Each Gov. college has different criteria to take the admission After giving the improvement exam you can get the admission in any of the college if you meet the eligibility For example to apply in  IITs, NITs, IIITs, GFTIs you require minimum 75% in class 12th as a general category & 65% as a reserved category. You can check the eligibility to apply for IIT JEE exam with given below link.

JEE Main Eligibility

Good Luck!