Pay attention and show up.
I went to a union school in Tualatin Oregon (local 290) and my dad went to a PHCC school in L.A. a million years ago
Are you going to a PHCC school? You will get classroom training and hands on stuff. I hope your good at math.
I think a person has to really want to do this or he will quit.
I dont know your situation but even though I worked for my dad at the time I did alot of digging and drilling holes and the idea of going to class after work sucked but it pays off in the end.
You will learn about materials, sweat copper etc., how to size pipe, septic systems and other good stuff.
In the end your will have a trade that you can take anywhere and always have a job or learn the bussines end and start your own shop.
Oh yeah, when I was in school there was always some heat between new construction guys and repair guys. It was all in fun though.