A couple of weeks ago, a gaggle of freshmen at McCallum High School in Austin, Texas, pulled out a pouch the size of a clementine and began batting it back and forth between their feet.

“It took a minute for me to realize, Wait, this is hacky sack,” said Sondra Primeaux, 56, a teacher at McCallum. “I haven’t seen this in a while.”

Now she sees it constantly. Students circle up with a hacky sack during lunchtime, or get in a few kicks in the hallways after class. Primeaux has been having flashbacks to the Phish and Grateful Dead shows of her youth.

“One of the boys was like, ‘Where can I get one?’” she recalled. “I said, ‘1992.’”

Once the domain of mellow Gen X-ers in the ’80s and ’90s, the hacky sack is experiencing a renaissance at the hands — well, the feet — of Gen Z. High school students around the country are freshly enthusiastic about the toys, crocheted bean bags that once hung in the air like the scent of marijuana. Parents and teachers mostly seem glad to watch young people be entranced by something other than their phones.

This time around, hacky sack mania appears to have taken off in the Northeast before spreading nationally with the help of social media. The sacks are technically called footbags — Hacky Sack is a brand name — but retailers of all kinds of thwackable bags are now racing to keep up with demand.