My D, a Senior at UMD, has worked with several Grad students on Research Projects over the past 2 years. In her experience, it is common (she would even say expected) that students would pursue Graduate Degrees at Institutions other than the one from which they got their Undergraduate degree.
UMD generally admits 425 Freshman Math Majors every year and graduates about 125 students with Math Bachelors Degrees every year.