Several years ago I was hired to take photos at one of these competitions, held in suburban New Jersey. Here's my report, Dance to the Music: the Kids Owned the Day.The children who enter these competitions train up to 30 hours per week, primarily on weekends and after school. Because children must compete in many styles — hip-hop, ballet, jazz and others — versatility is essential, and training can be rigorous to the point of extremity. Each competition bestows its own regional titles, and bigger events also offer national ones. Studios choose which competitions to attend based on careful consideration of cost, quality and competitiveness. Some students compete nearly every weekend during the season, which runs approximately September to July, and train at intensives and classes during the rest of the year.There are no official figures about how many children are involved in competition dance nationwide, but the number of national competitions has ballooned into the hundreds since the 1980s. In the late 1970s, one of the first of the organizing companies, Showstopper, held competitions out of the trunk of a station wagon. Last year, 52,000 dancers participated in Showstopper, and its touring fleet included a semi truck that transported trophies alone.A turning point came in 2011, when Lifetime aired a reality show called “Dance Moms.” A number of dance-themed reality shows premiered in the previous decade — “So You Think You Can Dance,” “Dancing With the Stars” — but “Dance Moms” focused on relatable kids who aspired to be famous for their dancing, not adults. The show followed a Pittsburgh competition team at the Abby Lee Dance Company, reporting breathlessly on the wins and losses suffered by its team of preteens. “Dance Moms” emphasized drink-sloshing and hair-pulling by the team’s parents rather than the particulars of the students’ lives, but it made several young dancers, particularly Maddie Ziegler, now 15, into minor celebrities. The competition community almost unanimously considers the show in poor taste, but it normalized the idea of child stardom among competition-dance students, teachers and parents. When she was 11, Ziegler was cast by the musician Sia in a music video for her song “Chandelier.” The video featured Ziegler as the sole performer, doing pirouettes, splits and kicks with a series of fierce facial expressions.When I started dancing professionally four years ago, dancers I worked with would sometimes make one another laugh in rehearsal by whipping out old competition moves: preposterously wide smiles, coquettish shoulder tilts. As adults looking for dance jobs in New York, they had hurried to leave these overblown faces behind, like a newscaster trying to scrub herself of a regional accent. They wanted to be modern dancers, and maximal facial expressions aren’t stylish in the world of concert dance, which is still the purview of college dance programs and conservatories. When competition dancers enter college or seek jobs in the modern dance world, they tend to tone down their “fire,” as one former competition dancer put it, to fit in. She was a national-competition titleholder while in high school, but now she treated her competition past like a secret. She wanted to join a modern dance company, and competition dance is often considered better suited to music videos, concert tours or cruise ships. She felt that some of the companies she wanted to join, which performed exclusively in theaters, looked askance at her background. As mainstream as it has become, competition dance is still a distinct dance subculture, revolving around pop music, hard-hitting choreography and young female adherents. “It’s a different world,” Melinda Wandel, a mother of an 11-year-old competition dancer, told me.