 However, while the enrichment and/or acceleration of curricula is considered to be a major benefit to high-track students, lessons taught in low-track classes often lack the engagement and rigor of the high-track lessons, even considering that low-track students may enter class with lower academic achievement.Oakes (1985) found that in high-track classes, teachers often used course materials and taught concepts which required extensive critical-thinking skills, whereas teachers in low-track classes tended to draw heavily from workbooks and rarely assign work that required critical thinking.In general, curricula of high-track courses are much more intensive and in-depth than those of low-track courses, as would be expected by differences in students' academic readiness.