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. Teachers also report spending less time addressing disciplinary issues in high-track classrooms than in low-track classes, which leads to differences in content coverage. Importantly, research finds that instructional differences across track levels goes beyond what would be expected based simply on differences in student readiness. For example, In English language arts classes, Northrop and Kelly (2018) found that in 8th grade low-track students read less challenging texts than students of similar achievement in grade-level classes, part of a pattern of more skill and strategy instruction and less literature analysis.