Using the Korean Education Longitudinal Study(KELS) 1~4th wave data from the Korean Educational Development Institute(KEDI), this study longitudinally examined middle school students’ educational plans and transitions to a special-purpose high school(SPHS). This study constructed the stacked datasets across three time points (7th grade, 9th grade, and entering high school) by collecting information on students’ academic career transitions to a SPHS during their middle school years. Then, this study examined conditional probabilities on students’ academic career transitions, consisting of making a plan for SPHS admission, preparing the SPHS throughout middle school years, and finally entering a SPHS. Findings suggest different opportunity structures for academic career pathways to a SPHS depending on when students began to prepare for SPHS admission. While many 7th graders began to prepare for SPHS admission, most gave up their plan before 9th grade. If they were on track to SPHS admission through 9th grade, they were more likely to enter a SPHS than those who began to prepare for SPHS admission in 8th or 9th grade instead of 7th grade. This study also suggests that students’ gender, parental education, family income, and school areas affected opportunity structures for students’ academic career pathways to a SPHS. Findings related to the effects of family background confirmed previous studies on the horizontal stratification between the SPHS and general high school(GHS). This study also suggests that educational inequality occurred not only in the stage of entering a SPHS but also throughout students’ academic career pathways to a SPHS.