Hi Shri Krishan, 

Students who are in class 12 can apply for SX stream in KVPY, provided they should have obtained 75% (65% for SC/ST/PWD) in class 10 in both Maths and Science and 60% (50% for reserved categories) in 12th class

There is no any age limit to apply for KVPY exam. Candidates studying in class 11, 12 and UG first year are eligible to apply for SA, SX and SB streams, respectively. You can check the further eligibility with the given below link.

https://school.careers360.com/articles/kvpy-eligibility-criteria

Good Luck!

dear student

For Stream SX:

1.Candidates studied in XII Standard (Science Subjects) in the academic year of 2018-2019 can appear.

2.Candidates have to obtain minimum 80% marks for Gen category & 70% marks for SC/ST/PWD category in aggregate in Science & Mathematics subjects in High School Examination.

3.Candidates have to score at least 60% marks (50% marks for SC/ST/PWD) in aggregate in Science Subjects in XII Standard.

4.Students can join the undergraduate programme in Basic Science (B.Sc/BS/B.Stat./B.Math./Int.M.Sc/MS) in the academic year 2019-2020

hope it helps......