Most school-issued IDs are not
acceptable, in fact, because they don't have an expiration date. I know, that makes no sense, either. The expiration on your driver's license isn't there so that the DMV can determine whether or not you've spontaneously become another person, after all. Some schools are issuing separate IDs that do have expiration dates, but obviously that's a lot of extra time, effort and money that can really stretch an already thin school budget. (Walker also did his level best to defund the schools.)
Is this the one I heard about that sent mobile units out to rural areas where they closed the offices that could help people get the necessary ID cards and had ended up only issuing a handful of IDs?
There was a scandal a couple of years ago about DMV closings throughout the state, which might be what you're thinking of. DMV locations in predominantly Democratic areas were either closed or had their hours cut, while locations in largely Republican areas were not affected. I did hear about voters' rights groups arranging for transportation to more distant DMV offices for those that would have trouble reaching them to get a state ID card, though I don't recall anything offhand about mobile offices going out to them.
Unfortunately, since his presidential run imploded, Walker's been making noises about running for governor again even though he said he wouldn't do that.
On the other hand, all the polls I've seen indicate that voters around here are sick to death of him, so his handlers might still talk him out of it.