While most colleges do not require their applicant to take SAT Subject tests, but some highly selective schools do it often such as Ivy schools and MIT.  MIT requires two SAT Subject tests, one Math and one science,  choose from Bio, Chem or Physics according to the major you are interested in.

So mostly only those high achieving students are taking SAT Subject tests,  particularly for SAT Subject Science.   Therefore,  the average scores for SAT Subject Tests are significantly higher than that of SAT 1.  For example,  the average score  of Physics SAT Subject Test is around 650, much higher than that 500 of SAT 1.

Most colleges do not publish their SAT Subject Test admissions data.  From the data available online,  we can see MIT seems to have the highest SAT Subject Tests scores, about 50% of its admitted applicants scored between 720 and 800 on SAT Subject Tests in Science. followed by Princeton with the same kind of scores between 710 and 790.

In short, the good scores of SAT Subject Test will significantly enhance your chance for elite schools , even they may not be the decided factor.

note: This article is just FYI only,  all materials are from online.