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.

“Some tutoring has existed since the existence of schooling,” said Mark Bray, a professor of comparative education at the University of Hong Kong. “But what’s interesting is that in Hong Kong, the star tutors have found a formula to work pretty much in an industrialized way, with mass production.”

As if. With the students’ futures now riding on that one big test, the preparation and tutoring business has swelled. The bureau now counts about 2,600 registered private schools offering “nonformal curriculums” — the category that includes tutoring centers — in Hong Kong, more than twice the number of primary and secondary schools in the territory.

Modern Education alone has more than 50 centers, and an advertising budget of more than $1 million, according to Minnie Wong, a company spokeswoman.

The star system can be pretty lucrative. Antonia Cheng, who tutors for Modern Education and estimated that she had taught more than 100,000 students in the past decade, said some of the company’s most popular tutors earn millions of dollars a year.

“Only my students recognize me,” Ms. Cheng said. “So it’s not that awkward.”