Khan Academy

The math sequence from arithmetic through calculus is deep and well-built, though it's not a complete cross-subject curriculum on its own.

No setup beyond creating an account — lessons, practice, and feedback are all built into the platform.

Entirely self-serve; a parent can assign a course and check progress reports without teaching any of it directly.

Completely free with no premium tier, which makes it unbeatable on pure value regardless of what else it lacks.

Short videos and instant-feedback exercises keep momentum going, though there's no narrative or game layer to sustain motivation long-term.

Fully self-paced and free of any grade-package structure, so it slots into or supplements almost any other curriculum without friction.

Built entirely for independent, self-directed use with instant mastery checks.

There's no dedicated homeschool community or curated support layer — it's a general-purpose learning platform, not a homeschool program.

Self-paced mastery tracking helps some learners work at their own speed, but there's no built-in accommodation beyond that.