Khan Academy
FreeFree world-class courses from arithmetic to college-level math, science, economics and humanities: video lessons, mastery-based practice exercises and progress tracking, with no ads and no paywall.
Why we recommend Khan Academy
Khan Academy is what education philanthropy looks like when executed with software discipline: a nonprofit offering genuinely complete K-through-college courses — not samples — free forever, no ads. The mastery system is the pedagogical core: practice exercises adapt until you demonstrate proficiency, and the knowledge map shows exactly which prerequisite is blocking you. Teachers get real classroom dashboards at no cost.
Best use cases
Best for: students filling gaps the classroom moved past too quickly, adults relearning math for a career change or standardized tests (the official SAT prep lives here), homeschooling backbones, and parents who want to understand what their kid is stuck on. AP-aligned courses track US curricula closely.
Honest limitations
Strongest in math and hard sciences; humanities coverage is thinner and less exercise-driven. The format rewards self-motivated learners — there is no cohort or deadline pressure unless a teacher assigns work. Advanced university-level topics beyond intro courses are out of scope.
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