He‘s german and Trust me finding a Security issue in german School Networks is not a big deal

That's right, when you do that in the US in any school the on-site cops come and arrest you. Initiative, competence and creativity are as a rule not prized in American education, conformity and athletic prowess are.

He meant that the networks often aren't secured at all, so it's very easy to break into them.

well I basically meant it differently, but that's bad aswell..

American here. Ditto (source: kicked out of high school and college for violation of TOS^H^H^H Acceptable Use Policy)

Out of curiosity, what did you do that was so bad as to get you kicked out of school twice?

In High school I discovered the admin's secret account password was "god". (1995 maybe? I was 15)

In college (1997? I was 17) I downloaded the source code of the unix client for back orifice. I read some of the source because I was interested in socket programming and reading Unix Network Programming. I compiled it, and deleted it without running it.

They were on edge because "god" from high school called to warn them about me.

Did the admin literally watch Hackers and use that password as a goof

It doesn't even have to be bad. I was very nearly kicked out of my middle school just for booting from (!) my own live Linux USB drive on a school computer.

Absolutely. Did not mean to discount his obvious natural talent!