Solution - get someone with a valid handicap sticker/license to use the slot next to her driver side door and park close enough the door won’t open far enough for her to enter the vehicle...
Actually, I’d favor getting two someones, one to park on either side. Then leave both vehicles there. For hours.
A lot of people don’t realize what those spaces are there for. A few years ago I worked with a lady who was wheelchair bound. She had a specially equipped van that allowed her to drive herself around. The side door of the van was equipped with a ramp that was her only access into and out of her vehicle. If someone parked in the striped area or parked too close on that side, she could not get back into her vehicle. A single parking space is NOT wide enough to accommodate the ramp.
Even if the spaces in the school parking lot aren’t used regularly, they should be left open and available.