What's considered a good score?

I got 720 on biology last year(molecular). Out of 800, that seemed good at first glance, but my percentile was 70th or somewhere around there. I’m taking two more this coming June(math 2 and chem) and I just wanted to know what sort of score I should aim for. I’m not super worried about it since most of the colleges I’m interested in don’t require a subject test, but a good score would obviously be to my benefit. Thanks in advance!

I would not worry about the percentiles. Relatively few colleges request/require Subject Tests. As a result, those that do take a Subject Test tend to be a self selecting group, so the percentiles are not going to be high. As to what is a good score? Depends on the college. For top colleges, 700+ certainly is in the ballpark, but that is only one small part of the admissions packet.