The three policies are genuinely different
Test required means you must submit scores. MIT reinstated this requirement after research suggesting scores helped it identify students who would succeed in its curriculum, particularly from under-resourced high schools. Georgia Tech and UT Austin also require scores.
Test optional means the college will consider scores if you submit them and will not penalise you if you do not. This is now the most common policy, and it puts a real decision in your hands.
Test blind — sometimes called test free — means the institution will not look at scores under any circumstances. WPI and Cal Poly San Luis Obispo are both test-blind. Sending scores to these schools has no effect whatsoever, positive or negative.
The decision rule
Find each school's published middle-50% SAT or ACT range, which appears in its Common Data Set and on this site's profile pages. If your score is at or above the 25th percentile of that range, submit. If it is below, withhold. That is nearly the whole rule.
Decide school by school rather than adopting one policy. A 1380 is above the 25th percentile at Purdue and Miami University, inside the range at Michigan and Cal Poly, and below it at MIT, Stanford, Rice and Carnegie Mellon. The same score should be submitted to some of your schools and withheld from others.
One nuance: some merit scholarship programs and honors colleges still require or reward test scores even when admission is test-optional. The University of Arizona's automatic merit awards are partly score-driven. If you are chasing merit aid, check the scholarship requirements separately from the admission policy.
What carries the application without scores
When you withhold scores, weight shifts onto your transcript — specifically course rigor, grade trend and performance in courses relevant to your intended major. An upward trend matters. So does having taken the hardest available math and science sequence if you are applying to engineering.
Essays and recommendations also carry more. This is worth planning around: if you are going test-optional at your target schools, budget real time for essays rather than spreading thin effort across fifteen applications. Eight well-written applications beat fifteen rushed ones, and that gap widens without scores to fall back on.
