Lattner starred in both football and basketball at Fenwick High School where he graduated in 1950. Fenwick, along with other Chicago-area Catholic schools, was a training ground for Notre Dame and Big Ten football programs, and Lattner held offers from top college football programs across the country. He initially considered the University of Michigan because head coach Bennie Oosterbaan ran the single wing offense, a scheme that fit Lattner well at Fenwick. Lattner eventually chose Notre Dame, which offered a Catholic education and the highest level of competition.