With an acceptance rate around 20%, Williams College mails out a lot more rejection letters than acceptance letters. Those students who do get in all have strong grades and test scores. In the graph above, the blue and green dots represent accepted students, and you can see that most students who got into Williams had averages of A- or higher, SAT scores (CR+M+W) above 2000, and ACT composite scores above 30. Good numbers, however, aren't all that is needed to get accepted. If you look at the red on the graph, you'll see that a lot of students with 4.0 GPAs and high test scores were rejected.
Williams College, like all of the country's top liberal arts colleges, has holistic admissions, so successful applicants need to have strengths that go beyond empirical data. Competitive applications should have a winning essay, strong letters of recommendation, and interesting extracurricular activities. As a few of the data points above illustrate, strengths in some of these areas can compensate for grades and test scores that are a little less than ideal.
To learn more about Williams College, high school GPAs, SAT scores and ACT scores, these articles can help: