Hello aspirant

Yes there's an option where you can give exams in science stream through open board.

1. You can go for open board like NIOS  for your class 12.
2. You can take admission in an open school under CBSE board and then give Board exam from it as a private student.
3. You can also study in an open school and tie up with another school from cbse curriculum as a private student and then give exams.

Hope this helps