B School that Allows Undergrad to take Grad Courses

[SophiaPrincess]

Thanks to the advice on this forum, I will soon complete my bachelor's degree with three years of unused Pell Grant remaining.  If I postponed graduation, could I continue taking courses at another university beyond what is required to graduate?  If so, does anyone know an accredited business school that will allow an undergraduate student to take graduate courses? My goal is to transfer these graduate business courses into an accredited MBA program, ideally AACSB but I am open.  My current university will allow me take a limited number of graduate courses with a waiver but they do not have a graduate school of business so the courses would not help me obtain an MBA.

Thank you.