The epidemiological and randomised trial of 41 classrooms in 19 schools (in 1985) found that GBG was effective for all students, especially for highly aggressive male students. A follow-up study was conducted when the cohort was 19-21 years old, and researchers found significant positive effects of the experiment on health outcomes, such as a reduction in drug abuse, smoking, alcohol abuse, criminal behaviour and suicidal thoughts (Kellam et al., 2011). In a standard classroom, drug abuse, antisocial behaviour, and violent and criminal behaviour for highly aggressive males were 83%, 100%, and 50%, respectively. Whereas in a good behaviour classroom, drug abuse, antisocial behaviour, and violent and criminal behaviour for highly aggressive males were 29%, 40%, and 24%, respectively (Kellam et al., 2011). Building emotional self-regulation skills in children at a young age results in positive health outcomes in adulthood (Kellam et al., 2011).