You are right in that it last for four calendar years. However, you are merely trading Fall/Freshman for Spring/Senior. You could also have your child postpone until then next calendar year. In that case, you would have:
- year 1 : spring of freshman + fall of freshman
- year 2: spring of sophomore + fall of soph
- year 3: spring of junior + fall of junior
- year 4: spring/fall of senior
