This study determined whether participation in an accelerated curriculum (specifically, the International Baccalaureate [IB] program) upon entry to high school is associated with increases in stress and/or associated with psychological problems. Data from self-report questionnaires were collected at two time points (summer after eighth grade, fall of ninth grade) from 134 freshmen entering three high schools. Results indicate that ninth-grade students in the IB program reported more perceived stress than students in general education, at levels higher than what was present before the students began high school. Despite this increase in stress, the psychological functioning (life satisfaction, psychopathology, and social anxiety) of IB students was statistically similar or superior to the mental health indicators reported by their peers in general education. The main effects of time, gender, and academic program are also discussed in the context of prior research on students' adjustment during the transition to high school.