This study seeks to explore whether unregulated school choice has the potential to diversify the high school curriculum, as elitist conservatives and neoliberals in Korean argue. Making use of qualitative research methods, this paper examines how national curriculum policies are implemented at two selected high schools (high-achievement 1, low-achievement 1) in a non-HSEP area. Elective curriculum and ability grouping, as two core policy measures of the current national curriculum, are intended to overcome the monopolized curriculum implementation that has plagued Korean education. However, the study finds that the term "curriculum diversity" in the document of national curriculum, rather than indicating inclusiveness, actually means "curricular variety" and "differentiation of curriculum" through electives and between-classroom ability grouping. While the mandated elective curriculum appears on the surface to realize students' career aspirations, it actually turns out to emphasize particular subject matters thought to be fruitful for higher college entrance exam scores. In addition, a cream-skimming effect is observed as a result of between-classroom ability grouping that makes it difficult for teachers to implement prepared lesson plans, especially in classrooms with low-scoring students.