In Maryland, once your son is on active duty as a mid, he can go to the local MVA and obtain a Maryland driver's license. He should do this before his license expires in November. The one in Annapolis is open on Saturdays (no liberty during the week for Plebes), but only from 7 to 1. So, he may have to get a chit to go before noon meal formation to get there in time, but that's a ways down the road. If he's been driving for less than 18 months, then he'll be issued a Maryland Provisional License. He'll also be required to submit documentation to prove his identity and current duty station (check the Maryland MVA website for required docs) and take a vision test.
Or just extend the license under Wisconsin law covering active duty military - http://wisconsindot.gov/Pages/dmv/license-drvs/miltry-svc/active-duty.aspx
Or just extend the license under Wisconsin law covering active duty military - http://wisconsindot.gov/Pages/dmv/license-drvs/miltry-svc/active-duty.aspx