Water Tower Place’s new ban on unaccompanied minors started with some confusion among unaware shoppers on Friday.

“I’m 26,” a woman told a security officer after being asked if she was a teenager. “Are you kidding me? Yeah, I’m 26.”

The officer was one of a half dozen manning the main entrance as the Magnificent Mile shopping center’s new “parental guidance required” policy went into effect, barring youngsters on Friday and Saturday evenings starting at 4 p.m.

Mall executives and Chicago cops looked on Friday as Water Tower public safety officers asked for IDs from any young-looking people trying to get inside.

Anyone under the age of 17 was told to stay with their parent or guardian, or turned away if they weren’t with a “supervising adult” who was at least 21. Accompanied minors were given blue wristbands to wear inside.

An announcement over the intercom system at 3:45 p.m. had alerted young shoppers they had only 15 minutes left at the mall if they weren’t with an adult. That was the final of several announcements made starting at 3.

The new rules were implemented until further notice “to eliminate disruptive behavior” by mobs of teens, mall managers announced this week. The change comes days after the latest in a string of chaos caused by young people in and around the ritzy mall.

Earlier this week, two teenage boys were charged with felony aggravated battery and mob action in connection with a Dec. 29 attack in which about 50 teenagers beat three people at the State/Chicago Red Line platform on the Near North Side.

“In an effort to eliminate disruptive behavior by unsupervised youth, we made the difficult decision to implement a curfew program,” Mitch Feldman, senior general manager of Water Tower Place, was quoted as saying in a news release.

Though officials said the policy would be “strictly enforced throughout the shopping center property, including exterior entrances,” the new approach could be tough to implement at a shopping center with multiple entrances, a theater and underground parking lot.

A walk through the eight-level mall Friday evening showed just as much, as groups of unsupervised teens strolled from store to store.

Ald. Brian Hopkins (2nd) said earlier in the week that Water Tower Place has been a “Michigan Avenue staple” for more than 40 years, and he didn’t mind if firm rules were needed to keep the mall safe.

“Recent events involving large numbers of juveniles engaged in criminal behavior downtown have been organized and planned on social media,” Hopkins wrote in an email to the Sun-Times.

“Frequently, we have seen Water Tower Place specifically listed as the rallying point for a large group to assemble with the intent to engage in mob action. This new policy will help Water Tower management curtail this activity.”