Finally, on a selfish note, I wrote an extensive review piece on this topic (Harden, 2014, "A Sex-Positive Framework for Reseach on Adolescent Sexuality" in Perspectives on Psychological Science), and I would, of course, be happy if the authors included a reference to my paper in their Introduction or Discussion.
**We did not keep an exact count of the number of students approached about the study, but we estimate that we approached about 375 students.