Understanding college admissions data can feel overwhelming, especially when acceptance rates and test-optional policies only tell part of the story. This guide explains how families can use the Common Data Set (CDS) to look beyond headlines, interpret Early Decision and testing data more accurately, and make smarter college planning decisions with real context and strategy.
If college admissions feels confusing, that is not because you are missing something obvious. A lot of public college data looks simple, but the most important details are usually underneath the headline.
A college’s overall acceptance rate may combine Early Decision, Regular Decision, athletes, institutional priorities, and waitlist activity. A test-optional school may enroll a class where nearly half, or far more than half, submitted scores. A college may say it does not consider “demonstrated interest” while still offering a binding Early Decision plan that should matter a lot in strategy.
That is why the [Common Data Set](Commondataset Home - Common Data Set) is useful. It is not a marketing page. It is a standardized reporting format that lets families look in the same places at different colleges and ask better questions.
Start with Section C1. This is where colleges report first-time, first-year applicants, admitted students, and enrolled students. The basic acceptance rate is simple: admitted students divided by applicants. Brown’s 2024-25 CDS, for example, reports 48,904 applicants and 2,638 admits, or about 5.4%. Vassar’s 2025-26 CDS reports 11,118 applicants and 2,327 admits, or about 20.9%.
Those numbers are useful, but they are only the first stop.
The next stop is Section C21, Early Decision, and C22, Early Action. This is where parents can see whether the overall rate is hiding a very different early-round story. Brown’s 2024-25 CDS reports 6,251 Early Decision applications and 898 ED admits, or about 14.4%. If you subtract those from the overall pool, the remaining admit rate is about 4.1%. Brown’s own admissions page cautions families not to assume that applying ED automatically improves chances, and that warning is important. ED pools often include recruited athletes, unusually strong fits, and students with clear institutional priorities.
But that does not mean ED is irrelevant. Early Decision is binding, and [NACAC describesED](NacacnetEarlyto Rise, Early to College? Early Applications in the Admission Process -National Association for College Admission Counseling (NACAC)) as a commitment to attend ifaccepted. In practical admissions strategy, that commitment matters. It is oneof the clearest ways a student can show that a college is truly first choice.The smart conclusion is not “ED is magic.” It is: “If this college is genuinelyfirst choice, and the family is comfortable with the financial-aid tradeoff, EDmay be one of the most important strategic choices in the process.”
Vassar is a helpful example because its CDS says “level of applicant’s interest” is not considered, but it still offers Early Decision. In the 2025-26 CDS, Vassar reports 1,046 ED applications and 402 ED admits, or about 38.4%. The remaining pool works out to roughly 19.1%. That does not prove a clean causal advantage for every student, but it does show why parents should not confuse the C7 “level of interest” checkbox with the strategic significance of a binding ED application.
Testing is the other place where parents often misread the data. Section C8 tells you the school’s testing policy for a future admission cycle. Section C9 tells you how many enrolled students in the reported class submitted SAT or ACT scores. Those are related, but they are not the same thing.
Brown is a perfect warning here. Its 2024-25 CDS shows that 61% of enrolled students submitted SAT scores and 24% submitted ACT scores for the Fall 2024 entering class. But Brown’s current admissions page says it returned to requiring SAT or ACT scores for first-year applicants beginning with the 2024-25 admission cycle. So a family reading only last year’s enrolled-class score data could make the wrong testing decision.
This is why we tell families to preserve optionality early. If your child is still building a list, it is usually wise to [schedule a proctored SAT or ACT diagnostic](/proctored-exams), compare both tests, and [build a start-to-finish testing plan](/test-prep) before deciding whether testing will matter. Policies vary by school, and the ACT itself is changing; for more context, see our posts on the [new ACT format in 2025](/blog/new-act-format-in-2025) and the [enhanced ACT](/blog/everything-you-need-to-know-about-the-enhanced-act-thus-far).
One technical point matters: the SAT and ACT percentages in C9 are not perfectly separate buckets. Some students submit both. So adding the two numbers gives you an approximation, not an exact count. At many test-optional colleges, most students submit one testing path, so the sum is often a useful estimate of how much of the enrolled class had testing in the file. But do not pretend it is mathematically exact. If the numbers add to more than 100%, as they do at MIT, you know there is overlap.
Parents should also be careful with score ranges. In a test-optional environment, the middle 50% scores in C9 usually describe the students who submitted scores, not the entire enrolled class. That can make the published range look intimidating. A score below the 25th percentile is not automatically fatal, and a score above the median is not automatically decisive. The real question is whether the score strengthens the student’s academic story in context.
A simple parent workflow looks like this:
1. Find the college’s latest CDS and open Section C.
2. Use C1 to calculate the overall admit rate.
3. Use C21 and C22 to separate Early Decision, Early Action, and Regular Decision where the data allow it.
4. Use C7 to see how the college says it weighs rigor, grades, testing, essays, recommendations, activities, and interest.
5. Use C8 and the current admissions website to confirm the testing policy for your child’s cycle.
6. Use C9 to understand how common score submission is among enrolled students.
7. Turn the data into a plan, not a panic spiral.
The Common Data Set will not tell you whether your child will be admitted. It cannot read essays, school context, recommendations, intended major, institutional priorities, or the way a student’s interests fit a campus. But it can help you stop treating college acceptance rates as headlines and start treating them as evidence.
That is a much better place to begin. And if you want help turning that evidence into a real list, testing calendar, and early-round strategy, our [college advising team](/college-advising) can help you think it through, or you can [contact us](/contact) to set up a planning call.
FAQ
**What is the Common Data Set?**
The Common Data Set is a standardized reporting format used by many colleges to publish admissions, enrollment, testing, financial aid, and academic data.
**Which CDS section should parents read first?**
Start with Section C. It includes first-year admission data, early application plans, testing policy, and enrolled-student score ranges.
**Can I calculate a Regular Decision acceptance rate from the CDS?**
Sometimes. If a college reports Early Decision separately and does not also have Early Action, you can estimate the non-ED rate. If multiple early plans exist, the math gets less clean.
**Should I add SAT and ACT submission percentages?**
You can use the sum as a rough estimate, but not an exact figure, because some students submit both tests.
**Does test-optional mean scores do not matter?**
No. Test-optional means scores are not required. Strong scores can still help, and C9 can show how common score submission is among enrolled students.
