The Broadway audience is getting younger.

In an encouraging sign for a booming but ever-fretful industry, the Broadway League reports that the average age of the Broadway theatergoer last season was 40.6 — not exactly adolescent, but the lowest it’s been since 2000.

The trend is significant for a predigital art form that often worries about the age of its patrons. It appears to reflect the large number of family-friendly shows on Broadway, which last season saw the openings of “Frozen,” “Harry Potter and the Cursed Child,” “Mean Girls” and “SpongeBob SquarePants,” as well as the continuing runs of “Aladdin,” “Anastasia,” “Dear Evan Hansen,” “Hamilton,” “The Lion King,” “The Play That Goes Wrong,” “School of Rock” and “Wicked.”

Fifteen percent of all theatergoers were under 18 years old, the report found. Musical audiences were much younger than play audiences — the average age at a musical was 39, while at a play it was 51.5.

“The trend is real — it’s not just a fluke,” said Charlotte St. Martin, the president of the Broadway League, which has made a concerted effort to introduce young people to theater, in part by bringing high school sophomores to shows. “And it’s not a big surprise when you look at the offerings. We just launched our fall program, and there are now 17 shows that teachers say are acceptable for 16-year-olds, which tells you something — 10 years ago we might have had five or six.”