Should math be compulsorily opted in Classes 11 and 12 in order to apply to a T20 college in the USA? What should be done if the course was not taken? Will a high SAT Math 2 subject test score suffice? [INDIA]
Most selective US colleges & universities require 4 years of high school math.
For a US student, yes. For an international student, it depends.
If your school follows the GCE Advanced Level curriculum, and math is not one of your subjects, then no. So it really depends upon the context of the HS curriculum.
I had Math until Class 10 which included Pre Calculus, Advanced Algebra, and Trigonometry. I got a high score in MATH 2 Subject test. Will taking an online certified AP Calculus BC Course help in any way? What else could be done? (I study in a school which follows the CBSE curriculum)
What is your intended major?
Biology
Well, for Ivies, count on needing rigorous math and science, for a stem major. A high SAT math2 does not replace these courses, over the school year.