In this study, we aimed to analyze Irish educators' differentiation practices and their relationship to teachers' sense of efficacy. We examined teachers' (N = 470) reports of their curriculum modification practices and their provision of challenge or choice. When their students had mastered the required class work, more than half of teachers were willing to substitute assignments on a weekly or daily basis for both their average and gifted students. However, the frequency of differentiation was not high in practices that eliminate mastered curricular material or allow students to work at their own pace, which would allow gifted students to work at their ability level. More than 40% of teachers reported practicing these forms of differentiated instruction once a month or less frequently. Fifteen percent of teachers reported never engaging in these effective differentiation practices. Differentiation practice was positively correlated with teachers' sense of efficacy, particularly for instructional strategies.