It can add a common measure
MIT can read an SAT or ACT beside students from very different high schools. The score may clarify academic preparation when the local transcript is unfamiliar, but its meaning still depends on course access and performance.
It cannot replace curriculum
A 790 Math score does not replace calculus readiness, laboratory science or the ability to explain technical work. Admissions readers can see whether the student pursued the strongest appropriate sequence; a composite does not manufacture missing preparation.
It can reveal a section imbalance
MIT considers the highest section scores from the same exam and does not require ACT Science or Writing. A section-level plan is therefore more useful than repeatedly chasing a round total without diagnosing the limiting skill.
It cannot predict admission
Recent MIT reporting places SAT Math at 780–800 and Reading and Writing at 740–780 for the middle half of admitted students. The cohort contains admitted students, not a mechanical rule. Students below, inside and above a range can receive different decisions because the application is broader.
It can guide timing
Applicants self-report every sitting; official reports are not needed during review. The useful final sitting must leave enough time for the route MIT accepts and for the applicant to confirm that the checklist is complete.
It cannot freeze the policy
For MIT, current first-year policy describes the verified scope. Testing policies, optional sections and reporting instructions can change; the application term must remain attached to every operational decision.