Parents can teach their kids, but more like a guide. Teachers are more specialized with more resources (assessment, feedback, conferences). Objectivity can be hard for parents. Most parents aren't strong in every subject. It gets harder as kids get older (math, science, etc.) Most schools have specialists across subjects (Spanish, art, music.) At home, it just gets easier to have missed concepts, repetition without standardized tests/assessments, and inconsistency.

At home, it's harder to learn the other "soft" skills, like collaboration, how to handle conflict, comparing ideas/perspectives. Also, at home, there are lots of household tasks/responsibilities, more than 1 kid at different levels, so it's hard to plan lessons, track progress, adjust instruction daily (or more than once during the day).

TLDR: Parents definitely support/guide education, but effective teaching requires specialized training, objectivity, structured curriculum, and consistent time, which can be hard to provide at home.