"In the HLM (Hierarchical Linear Modeling) analyses for students in grades eight, 10, and 12, drug testing (of any kind) was not a significant predictor of student marijuana use in the past 12 months. Neither was drug testing for cause or suspicion."
Source
Yamaguchi, Ryoko, Lloyd D. Johnston & Patrick M. O'Malley, "Relationship Between Student Illicit Drug Use and School Drug-Testing Policies," Journal of School Health, April 2003, Vol. 73, No. 4, p. 163.
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