Yes, most places want one of the general tests as well, not instead of. But honestly, there were only a few places we looked at that asked specifically for SAT2 in math, many more places just asked for a couple SAT subject tests, and many times that was “optional” but we read it as send them if they’re good scores.
Though honestly, many, many places have changed to test optional, especially now with the pandemic, so this all might be outdated advice anyway. I think the days of emphasis on the tests are in the past- my kids’ feeling was that a very low score would hurt, but otherwise a good score didn’t add much, as many kids can achieve that. One huge exception is scholarship-related stuff- that is totally different, and we don’t have much experience there.
