I assume he means subsidized by the value that Google is getting out of the sales other than the purchase price (because it increases Chrome usage which increases Search usage). I suppose he's not technically wrong (even if it's an indirect subsidy) but it's a bizarre usage of the term and it could apply to a LOT of device vendors.
I think it's fair to say that if your kid comes home with a ChromeBook that you didn't purchase, it's being subsidized somewhere. My local high school just issued them to all freshmen. What I find a bit odd is that if there is any paperwork involved, it's not "Do you give us permission to lend a laptop to your child?", it's "Your child must sign this pledge not to abuse this device." I support the program, but the responsibility goes two ways, and I expect the school district to advocate student privacy over the lure of "free stuff."
I don't think Google is giving them away (at least not in the US). This would have been funded by the school district. In my area (North Carolina), some have chosen Windows, some tried Ipads, and some are using Chromebooks. Generally peaking ,the ipads fair the worst and the trend is moving in favor of Chromebooks. Even if the hardware is free, there is still the need for an administration license, too.