Having worked in higher education for a number of years, I can tell you for a fact that the college I worked at most certainly kept up-to-date antivirus software, and we never had a virus problem on school-owned machines.
What schools can’t control is what students do to their own machines - and on those, yes, I saw malware.
Sorry, just had a different experience.
The computer in question was running Windows 98 and MS IE 5. Not Windows 98SE, the original Windows 98 - already a year out of mainline Microsoft support at that time.
For all intents and purposes that PC was placed in her classroom with a pre-installed rootkit.