Anki

Anki is flashcard software built around spaced repetition. You rate each card as you review it, and the scheduler decides when to show it again: material you find hard returns within a day or two, material you know well drifts out to weeks and then months. The effect is that revision time concentrates on what you have not learned yet instead of being spread evenly over things you already know.

The practical case for it in a homeschool is memorization that has to stick across years rather than until Friday. Latin and modern language vocabulary, multiplication facts, chemical symbols, historical dates, anatomy, music theory intervals, spelling rules. A student who reviews for ten or fifteen minutes a day holds far more of it than one who crams before a test, and the daily queue makes the habit self-managing because the software decides what is due.

Cards can carry images, audio and LaTeX, which matters for language pronunciation and for math notation. Shared decks contributed by other users cover most standard subjects, so a family can start without authoring anything, though home-made cards tied to your own curriculum usually work better. Anki is free on Windows, macOS, Linux, the web and Android, it is open source, and syncing across devices is free; the iPhone and iPad app is paid, and that purchase is what funds development.

Be realistic about the friction. The interface is functional rather than friendly, and the settings expose more scheduling detail than most families want to see. Writing good cards is a skill in itself, and badly written cards, especially ones that ask for a long list, feel punishing and get abandoned. Younger children generally need a parent to build the deck and sit with them for reviews; independent use realistically starts around middle school. And it only does one job. Anki drills recall, and recall is not comprehension, so it belongs alongside real instruction rather than in place of it.