<p>Extra time due to co-ops does not really count as extra school in terms of costs paid – the student would still be doing 8 semesters of school, even if s/he graduated after 9 semesters including the co-op semester. However, particularly in smaller schools or departments, there is the risk that a co-op semester may delay graduation an additional semester if required sequenced prerequisites at not offered every semester, and the co-op semester causes the student to miss one and have to wait a whole year to take it.</p>
<p>In general, four year graduation rates are not that high (for any major) except at the most selective schools. Delayed graduation often occurs because:</p>
<ul>
<li>The student cannot handle a full course load each semester.</li>
<li>The student enters needing remedial courses (engineering majors who are placed into precalculus will have a hard time graduating on-time).</li>
<li>The student changes majors late.</li>
<li>The student needs to repeat failed courses.</li>
<li>The student is not careful about fulfilling prerequisites.</li>
</ul>