IOWA CITY, Iowa (AP) – The University of Iowa is tightening the rules for incoming out-of-state students seeking in-state residency after beginning their studies. Officials say a record 317 part-time freshmen enrolled at the university for fall 2016. The Iowa City Press-Citizen reports that many of those nonresidents weren’t taking enough credit hours to trigger the higher, full-time tuition.

Out-of-state students who want to become residents must live in Iowa for at least a 12-month period and prove they moved to Iowa primarily for reasons other than higher education. The nonresident students previously had to show that they worked an average of 20 hours a week for those 12 months. Under the tighter rules, students enrolling after May 1 will have to show they’re working an average of at least 30 hours a week.