We also examined whether grade level was a moderator of substance use for middle school and high school adolescents (Table 2). As is shown, grade level moderates the effect of parental knowledge on other drug use (p <.05) and any drug use (p <.01), at the slope. Specifically, baseline parental knowledge is more likely to have an impact on decreases in substance use among middle school adolescents. At comparable levels of parental knowledge, there is a 26 percent increase in the slope of other drug use and 22 percent increase in the slope of any drug use for high school students when compared to middle school students. Average parental knowledge did not differentially predict substance use for middle and high school students at baseline (i.e., the intercept).
