In the US, at least, homeschooling is generally allowed. Some states don't have any requirements at all on who, how, and when a student can be homeschooled as long as a parent signs the right form. Some school districts let homeschoolers take a class or two without being fully enrolled.
For some students and some schools, being in school is actively bad for them, even worse than a fairly useless homeschooling experience. Some schools are just that bad.
The hard part is getting into college. You can take a test (the GED) that is meant to certify that you have an equivalent to a highschool education. Still, without a transcript, you will have to lean a lot on your resume (jobs, volunteering, internships) and personal statement.
For some students and some schools, being in school is actively bad for them, even worse than a fairly useless homeschooling experience. Some schools are just that bad.
The hard part is getting into college. You can take a test (the GED) that is meant to certify that you have an equivalent to a highschool education. Still, without a transcript, you will have to lean a lot on your resume (jobs, volunteering, internships) and personal statement.