https://en.wikipedia.org/wiki/Bloom%27s_2_sigma_problem

Bloom found that the average student tutored one-to-one using mastery learning techniques performed two standard deviations better than students who learn via conventional instructional methods[1]—that is, "the average tutored student was above 98% of the students in the control class".[1]:4 Additionally, the variation of the students' achievement changed: "about 90% of the tutored students ... attained the level of summative achievement reached by only the highest 20%" of the control class.

REMINDER: If you don't take advantage of tutoring in college, you're a fucking idiot.