Admin Access for Teachers or Not?

Should teachers have administrative access on their school-owned computers? In our district we have a mixed environment of Windows and Apples for teacher laptops. Years ago we revoked all administrative access on teacher laptops. Life from a tech-support perspective got much better!

All teachers were then using Window machines. There weren't clear guidelines on what was allowed to be installed. Teacher laptops were full of viruses, spyware, and software (personal versions of finance programs, Peer to peer sharing programs) that should never have been installed. Admin access was revoked and the support issues releated to these rogue applications were eliminated. We have since then brought on Apple laptops of which I have allowed administrator access. Teachers have the freedom to update and install educational software as needed. This has not caused problems like we saw earlier when access was open on the Windows laptops.

Now I am at a new era, where I would like to open this option back up for our teachers using Windows laptops. (We run both.) I can already hear our technicians telling me what a bad idea this is going to be. I will be arguing on the side of giving teachers the flexibility to use their laptops to its fullest extent which includes running an update when needed to iTunes, or Firefox, or whatever, or installing a great open source application they have found. I am considering the security risk and the support time involved if there are problems. However there are also support costs incurred when we have touch each machine to fix or add another application we'd like them to use.

Do I turn on the flood gates on teacher Window laptops and give them Administrative access despite what I know our technicians will tell me when I bring it up??? Do I allow this freedom for teachers to explore, update and install so they can use their laptops more fully, risking the added security breaches and support issues that will likely also occur? I can hear them arguing with me already.