Windows 7 : Deep Freeze or Antivirus?

Hi,

basically, I want to know if Windows 7 with Deep Freeze and no anti-virus is safe enough in a K12 school?

I’m preparing laptops with Windows 7 for students. Kaspersky anti-virus can not update itself if Deep Freeze is on. That cause computers to behave weirdly after a few weeks.

By creating standard accounts with strict policies and allow only Firefox as a browser, I should be able to reduce viruses.

Or should I do the opposite…Windows 7 with Anti-virus but no Deep Freeze?

Thanks in advance for your comments!