There is some evidence to suggest that the association between discipline and child behavior problems differs depending on ethnicity. Deater-Deckard and dodge (1997) found that mothers' harsh discipline in kindergarten was associated with higher teacher-reported externalizing problem for European American children in every year of their study, from kindergarten through 6th grade. By contrast, there were no significant association between harsh discipline at age 5 and later problem for African American children. Polaha et al. (2004) found that mothers' physical discipline was associated with lower levels of teacher-reported problems, but only for African American boys. Other researchers have not found any differences between these two ethnic groups, with both showing similar positive associations between physical discipline and child behavior problems.