Definitely agree they should be split up if possible. Octoprint and Home Assistant are both rather demanding on a Pi, particularly the Pi 3B.
I would however opt to run Pi-Hole on the Home Assistant device as there is a plugin built in for it, and Home Assistant is the kind of thing you would be more likely to leave on at all times.
I’m sure it varies from country to country, but here in Canada, at least Ontario, which is the only province that I am familiar with when it comes to teaching requirements, you would definitely need to attend teacher’s college, which is a two year program.