This study investigated the impact of several demographic and psychological variables on the academic achievement of 488, 12-15 year old adolescents in several secondary schools in Trinidad. Participants were two hundred and seventy males (270) and two hundred and eighteen (218) females randomly selected from each of the seven educational districts. Data were collected using three survey instruments and a demographic data sheet. Data were analyzed using MANOVA, mediation analysis using hierarchical regression proposed by Baron & Kenny (1986), Pearson''s and Spearman''s correlation. Post hoc analyses were carried out using Tukey''s HSD and effect sizes were reported using partial eta squared and Sobel''s test developed by Preacher & Hayes, (2004). Alpha levels were all set at the p < .05 level. The findings revealed significant main effects for age/cohort, gender and ethnicity. Both locus of control and self efficacy for academic achievement were found to be significant partial mediators in academic achievement. These findings are discussed within the socio-cultural and educational contexts of Trinidad.