Whatever amount they are getting from the publishers to do that is going to be less than the amount the publishers expect to get from the students because of it (plus all the expenses of building and maintaining the web portal).

The schools could just charge an avoiding corruption fee that is the same value as the kickback, tell the publishers to fuck off, and give the students a better experience that is also cheaper than the "recommended" one the publishers want to force them into to sell way overpriced books.