How the rankings work

1. Evidence, not stars

Star ratings mostly measure how much students liked a tutor. TutorRank instead reads every testimonial on a tutor's public profile and keeps only the ones that cite a concrete result: "went from a C to an A on her tests", "quiz scores rose from 70 to 90". Each one becomes a before → after data point on a 100-point scale.

2. Letter grades become points

A = 95, B = 85, C = 75, D = 65, F = 55; a plus adds 3 and a minus subtracts 3 (B+ = 88, A− = 92). Percent scores are used as-is. So "C to an A" = +20 points.

3. Tests count more than quizzes

Each data point is weighted by what it measures: test grades × 1.0, overall class grades × 0.9, quiz grades × 0.8.

4. High-end points are harder to earn

Raising a 90 to a 100 means eliminating your last mistakes — harder than fixing your first ones. Each point gained is therefore weighted by the band it's earned in: 60–70 × 1.0, 70–80 × 1.25, 80–90 × 1.5, 90–100 × 2.0. A 90 → 100 counts as 20 weighted points; a 60 → 70 counts as 10. Gains that span bands sum their parts. Scores below 60 are floored at 60 first — very low baselines are statistically noisy, and without the floor one dramatic anecdote would outweigh consistent evidence.

5. Many wins beat one big win

A tutor's Impact Score for a subject is (weighted evidence count)^0.8 × (average weighted gain)^0.2. The count is deliberately dominant: ten modest gains outrank a single dramatic story. With the same amount of evidence, bigger weighted gains win.

6. Value, and a price floor

Value = Impact Score ÷ hourly rate: how much proven improvement each dollar buys. Tutors who don't list a price aren't ranked — without a rate, their value can't be compared. We also rank only tutors charging $60/hr or more: this board is for choosing among serious, established tutors, and bargain-rate listings are a different search.

What gets excluded

Vague praise ("helped so much!"), ambiguous extractions, grades that went down, low-confidence readings, gains entirely below the 60-point floor, and tutors with no listed price. Excluded testimonials are stored, and every tutor page shows exactly which ones scored and which were excluded, so you can audit any ranking yourself.

Honest limitations

Testimonials are self-selected and unverified; a tutor with few reviews isn't necessarily worse, just less proven. Data is a pilot sample from Wyzant, Preply and SuperProf, refreshed manually. Always read the original profile before hiring.