South Dakota public universities are putting more energy than ever before into making sure freshmen return for a second year, but their bid to improve retention rates -- and with it graduation numbers -- has struggled in its early stages. The universities have overhauled the way underprepared students shore up their math skills, installed software that uses grade and attendance data to identify at-risk students early in the year, and required freshmen to take seminar courses that acquaint them with campus services and activities.