I had a similar level of access to my school's network when I was 12. It was really easy, just watch the teacher slowly peck-type her password. It was "teach". That gave me access to everything for her class.

Later on she had to log in to the admin account, and that password was "burger". It turned out to be the password for every admin account in every school in my district. I'm guessing they were all set up by the same guy, with a note saying, "make sure to change the password!"

I had access to EVERYTHING. But, I was a pretty good kid, so I just poked around enough to really verify that I could do anything and then I logged out and never logged back in. I was terrified that I was going to get in huge trouble just for accessing things I shouldn't have.