Seventy-eight (23%) of the 342 PVEs and 18 (100%) of the 18 SVEs in The Netherlands attended the conference. Of those
attending, 18 of the PVEs (23%) and 17 of the SVEs (94%) responded positively. The management of these schools made the
decision as to which classes would participate in this study. No information is available concerning how the management made
these selections. A total of 3499 students and 166 teachers from 198 classes in those 35 schools participated in the study. Since
much of the information concerning the learning environment—the primary point of interest for this study–was derived from the
teachers of these students, a partially or nonresponding teacher could cause missing data for all or most of the students in his/her
class. Data from 13% of the responding students were lost in this manner.