She considers the extra time she puts into organizing it worthwhile.
"It's good for them," she said. "It gives them a chance to shine, to show off a little bit."
This year's show on March 20 included 17 activities, including balancing-bar demonstrations, a choreographed routine combining gymnastics with the Macarena, jump-rope tricks, ball-handling demonstrations and ballet.
Deneen said she tries to keep the show fresh by adding something new every year. This year, the new feature was plate-balancing.
Gymnastics have remained the core of the event, she said.
That gives every fourth- and fifth-grade student an opportunity to demonstrate skills they've developed over the years in physical education classes, Deneen said.
"Everyone's allowed to be in it. There's no picking and choosing," she said.
The gym show has always been connected with a PTA meeting, and draws one of the biggest crowds of the year, Deneen said.
Putting on the show involves about a month of after-school practice sessions, she said.
It takes practice to come up with the routines and then perfect the performance, said fifth-grader Ryan Myers, who participated in his second gym show this year.
"It was fun. You got to do a lot of things in front of a lot of people," said Ryan, 10, of Williamsport, who did gymnastics and some fancy basketball handling at this year's show.
Classmate David Petway, 10, of Hagerstown, said he didn't mind giving up his free time, "because it's fun."
"The kids really want it," said David, who did gymnastics, vaulting, ball handling and a group parachute handling routine.
"It's a privilege," said fifth-grader Sherry Morris, 11, of Hagerstown, who did jump-rope tricks, the Macarena routine and gymnastics on the balance beam.
Most of the county's elementary schools have either a traditional gym show some variation, said Eugene "Yogi" Martin, who supervises the school system's physical education program.
"It's our way of sharing with the public what is done in the year as part of physical education," Martin said.
"The audience appreciates what the kids can do," said Martin. He said the county's physical education program is designed to be fun and help students develop skills and coordination.