About PrepCAT

About PrepCAT: how it works, and where it can be wrong

Updated

PrepCAT is an independent project made in New York City, for New York City families. It offers a free adaptive SHSAT practice test, practice questions and admissions tools. The name is Prep + CAT, and CAT stands for computer-adaptive test: the format the SHSAT uses starting in fall 2026.

PrepCAT is not affiliated with or endorsed by NYC Public Schools, the NYC Department of Education, or Pearson. We use “SHSAT” only to describe the test.

Original questions

Every passage and question on PrepCAT is written for PrepCAT and checked against New York State grade 6–7 standards. We do not copy questions from the official SHSAT practice tests, NYSED released tests, or other prep companies. We use the official materials only to understand the format. You can see examples on our SHSAT practice questions page.

How the PrepCAT estimate works

Method as of October 7, 2026. If it changes, we will update this section and its date.

1. Adaptive question selection

The PrepCAT mini test has 21 questions in 40 minutes: 11 ELA and 10 math. Every question has a difficulty level from 1 to 5, set by our writers. Each subject starts at average difficulty. After every answer, or after each passage set, PrepCAT re-estimates your child’s level from all of their answers so far in that subject and gives the question or passage set closest to it. That running estimate is the one in step 3, with a slightly stronger starting assumption, so a single early answer rarely moves the difficulty by two levels; in our simulations this was just as accurate. Every child gets the same mix. In ELA: a first reading passage set, a second reading set matched to the estimate (one of three), a Revising/Editing Part A passage with numbered sentences (one of two), and one stand-alone Revising/Editing Part B question, in the order of NYC’s 2026 practice tests. In math: 2 questions from each of 5 topics, with 7 or 8 multiple-choice questions, 1 or 2 typed answers and 1 other interactive question, close to the mix on the 2026 practice tests. This follows the approach NYC describes for the real SHSAT on its SHSAT page; NYC’s exact selection rules are its own.

2. A Rasch-style model

We place ability (θ, “theta”) and question difficulty (b) on one scale. Level 3 sits at 0, and each level up or down moves the difficulty by the same step. The chance of a correct answer follows a Rasch-style (one-parameter logistic) model:

P(correct) = 1 ÷ (1 + e−(θ − b))

When ability equals a question’s difficulty, the chance of a correct answer is 50%. It rises as ability moves above the difficulty and falls as it moves below.

3. The final ability estimate

After every answer, and again when the test ends, PrepCAT estimates θ separately for ELA and math from all of the answers so far in that subject, using an expected a posteriori (EAP) estimate. EAP combines the answers with a weak starting assumption that students are spread around the middle of the scale, so a short test with a few lucky or unlucky answers does not swing to an extreme. We keep that assumption weak on purpose: a stronger one pulled strong students' estimates about 20 points too low in our simulations.

4. From ability to a PrepCAT score

PrepCAT score = 480 + 55 × (θELA + θMath), rounded and kept between 200 and 800

A student in the middle of our scale in both subjects (θ = 0) gets 480. For example, θELA = 0.5 and θMath = 0.3 give 480 + 55 × 0.8 = 524. The 200–800 range is PrepCAT’s own display scale. NYC does not publish a fixed SHSAT score range.

5. How far off it can be

In our simulations, one 21-question test typically lands within about ±50 points of the student’s true level on our scale, and some results miss by more. Averaging several tests narrows the random part of that error: the average of three tests is typically within about ±30 points, which is why My Progress shows the average of the last three. Averaging cannot fix a systematic gap between our scale and NYC’s. Only calibration can.

6. Estimates from practice-test answers

The SHSAT score calculator can also estimate a score from the number of questions right on a full-length practice test. That estimate uses a different model, built on NYC’s own description of how raw scores turn into scaled scores; its method and error are explained on that page.

7. What it is not

A PrepCAT score is not an official SHSAT score, and it does not predict one exactly. We have not yet calibrated our scale against official results. When we can compare PrepCAT estimates with official scores, we will publish the measured error on this page.

How NYC scores the real SHSAT

On the real test, each question has a set difficulty, and the score comes from the student’s pattern of right and wrong answers compared with question difficulty. Starting in fall 2026, the score is re-estimated after each answer from all answers so far. Performance on each subtest is converted to a scaled score through a standardization process; the two scaled scores are added to make the composite score used for rank ordering. NYC does not publish raw-to-scaled conversion tables or a fixed score range. (NYC SHSAT page, “How will the test be scored?”). More on the new format: what’s on the 2026 SHSAT.

Cutoff scores

Cutoffs are the lowest scores that received an offer at each school in a given year. NYC Public Schools publishes them on its Specialized High Schools page. Future cutoffs will differ, especially after the switch to the adaptive test in fall 2026. See the SHSAT cutoff scores for 2022–2026, or compare a score with them in the SHSAT score calculator.

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