Unless the student comes in with a lot of useful credit (from AP or college courses taken while in high school), doing a co-op will extend the calendar time to graduation (i.e. 4.5 to 5 years to graduate) but not usually require any additional tuition-paying school semesters or quarters (i.e. still a total of 8 semesters or 12 quarters if you take full course loads, follow your major’s course plan, and do not fail anything). However, if your major at your school has tightly sequenced prerequisites which are not offered every semester, you need to be careful about choosing your semester off to avoid missing a once-per-year key prerequisite. In some cases, it may make more sense to do two separate co-ops in order to reset the fall/spring sequence so that you are in-phase with the usual offerings.