We designed a cross-sectional study that assessed, on one
hand, individual variables related to the students and, on
the other, variables related to their school environment.
Thus, there were two populations under study:
When it came to the schoolchildren, we obtained a representative sample of students enrolled in the sixth year
of primary education (age, 11.7 ± 0.4 years) in the city of
Logrono. ˜ We randomly selected 372 students from the 31
primary schools of the city, of which 329 (88.4%) agreed
to participate in the study. We excluded from the analysis
11 students that did not complete the questionnaires correctly, so the final sample comprised 318 schoolchildren. We
obtained the informed consent of their parents or guardians.
At the same time, we requested the collaboration of the
management of each of the schools (19 public schools and
12 charter schools). The study took place between February
and May of 2012. Participation was voluntary, adhering to the
ethical principles for medical research of the Declaration of
Helsinki. The study was approved by the Comité Ético de
Investigación Clínica (ethics committee for clinical research)
of La Rioja.