I am applying to a lot of reach schools (Brown, Williams, Swarthmore, Pomona) with a 32 ACT with essay and around a 4.2 W GPA. I am happy with my Common App essay and all of my supplements. I didn’t really realize SAT subject tests were a thing, and I thought that by taking the ACT with an essay, I didn’t have to worry about them. But now I’m realizing I made a mistake. How much will this hurt my chance at admissions?
If the colleges “recommend” SAT subject scores, not having them may be disadvantageous, but how much may not be knowable by those outside the admissions office. If you are in an environment where students and counselors are unlikely to know about colleges wanting SAT subject tests (e.g. a low SES high school where hardly anyone applies to colleges that want SAT subject tests, especially if you are first-generation-to-college and/or low SES yourself), then it may be more understood by the colleges why you do not have them. But if you are in a high SES high school where applying to colleges that want SAT subject tests is common, then it may be more of a disadvantage.
Did you take AP or IB exams? Some colleges will consider them in place of the subject tests. It varies by college, though. Check the admissions web pages.