I didn't know schools use them in the US! That's pretty cool. I think macs will get viruses one day, because it isn't unheard of that people get round 'password protected shit' why should the root pass be any different?

Anyway, the point people were trying to make about no one 'wanting' to make viruses for the mac is this:

The mac is harder to make a virus for
There are many PCs out there that are easier to infect and it is a wider range of people
Why would someone do something that requires A LOT more effort and get less benefits