To date, a couple of studies have identified a relationship between adolescents' self-concept, both academic and global, and their levels of school engagement. For instance, Murdock et al. (2000) found that 7th grade students holding higher academic self-concepts tended to exert higher levels of effort in 9th grade, as indicated by their frequency of doing homework, levels of school attendance, levels of participation at school, and effort in studying for exams. This relationship was identified in a sample of mostly Caucasian and African American students from the mid-Atlantic, and was found despite controlling for differences in students' achievement, relationships with peers and teachers, and perceptions of education in 7th grade. Likewise, a similar relationship has been identified between adolescents' global (not specifically academic) sense of competence and their level of emotional or affective school engagement in a sample of urban, African American junior high school students (Connell & Halpern-Felsher, 1997), although this relationship was found in a cross-sectional examination and therefore must be interpreted with caution.