Multiple questionnaire forms are used in all three grades; the question items featured in these analyses were administered to a random portion of each sample. Cases are weighted to take account of sampling design; weights are normalized so that the actual number of questionnaires (raw observations) is approximately equal to the weighted number. Weighted total numbers of cases for the analyses reported here equal or exceed 102,109 for 8th graders, 107,849 for 10th graders, and 107,421 for 12th graders. Significance tests and confidence intervals take account of design effects due to the stratified samples clustered in schools.