Are you the sort of person that participates in alumni organizations? Do you cheer on their sports teams later in life? Or do you simply view your school as a stepping stone in life that isn't as important? I'm aware there are a multitude of different ways to relate to a school, those are just examples.
This goes for any educational level: high school, college, grad school, etc.
Not at all, while I keep in touch with certain teachers/professors I have no desire to have an attachment to my alma mater for high school. The same is holding true for college. I am just not a fan of either administration, and find myself at odds with them and the way things are run, to the point where I've already decided neither will ever be receiving my hard earned money (willingly) after college.
To me, not important. Well, if I decide to go back to school, I'll need letters of recommendation and transcripts, so I guess important in that way. As far as alumni stuff goes, not important. I barely spent any time on campus when I went there. It might have been nice to spend some more time there, but I was always working.
I went to two different high schools and I went to two different universities. Of all of them, I'd be most likely to give my hard earned money to the Catholic school I went to in 10th and 11th grade. I had a great experience there and those teachers didn't make squat for money. But, I've never given any money, time or attention to any of them after I left. Probably never will either.