The slick entrance hall at one of Modern Education’s Hong Kong centers has the look and feel of a movie theater lobby, crowded with teenagers after school lets out. But the matinee idols in the portraits lining the walls aren’t movie stars — they’re tutors.

The exam-preparation business has become as fiercely competitive in Hong Kong as school itself. Cramming centers like the ones run by Modern Education jockey for business by turning their employees into celebrities, plastering their names and faces on the city’s buses, metro stations and billboards.