How tight should security be ? Network, workstations ?

I have worked in the IT field for a very long time…. and was recently asked to teach again in a local school’s adult education forum.
Never in my life have I been so frustrated working in a networked class room computer lab.
I could not run programs from a cd based disk, I could not install any program, could not make student folders.. not even on the instructors pc. Many accepted sub programs were not installed or availiable (Adobe Reader, Adobe Flash Player, Quicktime, etc.)
When is security too much ? When should you have to deal with network admin approval for accepted software ?
All the pc’s allowed an internet connection (Thank God).
I was even asked to teach an Ebay Basics and Advanced class. Ebay Turbo Lister was not accepted to be installed for the class.
When is security too much ?