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<p>Yes, there are, especially at co-op heavy schools like the Cal Polys, but that probably does not explain all or most of the late graduates. Most CSU students are not NMFs or others with elite-level academic qualifications from high school. (And the original question was framed in terms of semesters, rather than years, to exclude cases like your son who took only 8 semesters of school.)</p>
<p>When I went to college, when it was much less selective than today, the four year graduation rate was around 40% or less (versus 70% today). A lot of the students were taking more than 8 semesters because they were averaging lighter than normal course loads, and/or needed to take remedial courses (over half of freshmen had to take remedial English back then).</p>