For something to be truly learned (in pedagogical terms), it must not only be assimilated but then applied to new contexts and situations. The classroom is the optimal environment for students to practice and repeat information they've been taught. This is for two main reasons that teachers can and must deliver on:

• Students can feel only slightly more challenged than what they are already capable of
• Students can receive immediate and constructive feedback

"Active learning exercises", where students are asked to use knowledge they have just acquired in new contexts, are the most important measure of mastery in a pedagogical setting. When active learning exercises are designed to engage with the deep structure of the content they are engaging with, students are most likely to not only remember but apply what they learn in classroom settings.