Well first off, high school here is like college in that it's not compulsory, you have to test into it, and you have to pay for it. There's also various kinds, such as academic (where I am) that focuses on classes and learning; technical schools that focus on a specific skill set; agricultural schools, which have students learning how to work on a farm; and so on. The "more involved" teachers is probably referring to homeroom teachers. From the moment they enter, students are put into a specific class and then that class takes all their classes together. Their homeroom teacher is the one in charge of taking care of them as a whole, and also teaching them whatever subject they specialize in (homeroom teachers can be from any field). I often hear HR teachers have meetings with the parents (sometimes at school, sometimes visiting their home), and are a source of support and guidance for their homeroom.
In all seriousness, if I had a harem and someone found out, I would be arrested, fired, deported, and banned from Japan. Very obvious reasons why I have an army instead. >>
Sounds like quite the career! I, uh, don't have a harem of little Japanese girls actually, I have an ARMY BUILT OF THE JAPANESE YOUTH.
(I actually teach High School so they ain't so little lol, and I have male and female students.)