You guys blabbing on about student rights and discrimination are completely missing Jeff’s point. That sign on the convenience store is most likely not there simply because the owner hates students - it is there because the owner has had problems with large groups of students in the store before. The owner is now taking steps to control it. The fact that these types of signs show up all over the place means that students are generally causing a problem.
Instead of worrying about rights, worry about preventing the students from causing enough problems that such actions from store owners are necessary. Once a solution to that problem is found, there will be no need for these signs.