Substance use is a worldwide problem with increasing use among children and adolescents in the school systems. This study investigated the lifetime and current use of cannabis and alcohol in two contrasting school systems in Trinidad: Government Secondary Schools (GSS) and Servol Vocational Schools (SVS). A questionnaire was administered to 468 students (age 12-23 years) at three grammar-styled schools and two vocational schools in north, central and south Trinidad. Demographic data was collected on age, gender, family structure, religion, and peer -group effect. Twenty-eight percent reported lifetime cannabis use and sixty-one percent lifetime exposure to alcohol. The current rate of cannabis use was almost four and a half times more common among vocational school students. Both alcohol and cannabis was more commonly used by males in both school systems (95% CI 43.6 -56.4, ρ = 0.004). The age of onset of cannabis and alcohol use was statistically lower in government-assisted school students (T 2.36, df 95, ρ < 0.05, Τ 5.06, df 253, ρ < 0.001 and Τ 3.07, df 118, ρ < 0.01 respectively). Cannabis use was positively correlated with peer group usage, increased with age, and positively correlated with a non-intact family (X2 = 7.451, df = 1, ρ = 0.006). Alcohol and cannabis were more prevalent in vocational school systems, where cannabis was excessively used. Important contributory factors were family dysfunction, gender, age, and peer pressure. It is imperative that the Ministry of Education be sensitized about this growing problem and appropriate educational and preventative programs instituted.