I know it's a bit late but, 650 is not that low of a score. From talking with some of my professors, who got their degrees from Group I schools (PSU and Michigan), that was about the average subject test score (for american students with undergraduate degrees). I know it's too late to change your decision, but for others asking themselves a similar question with scores in the 620-680 range, I think the correct call would be to submit your scores. @svent Seems to be the one with the best sense here. They either assumed that you did not take the test which could be seen as a lack of effort or that you scored abysmally, both cases hurt your application.