The part of a sentence "gymnastics class" is correct and can be used in written English.
Example: I signed up for a gymnastics class at the local community center to improve my flexibility and agility.
He put Alexei in a gymnastics class.
Gisel still somehow manages to drive Tatiana to gymnastics class.
The group, scarves held aloft, resembled a rhythmic gymnastics class.
Maryse Wolinski went to a gymnastics class that morning.
I called and told a complicated lie about an after-school gymnastics class.
Writer describes her world, which ends at Chelsea Piers in the south, where she takes gymnastics class.
At 41, he had a mild stroke while at his daughter's gymnastics class and was diagnosed with diabetes.
Writer describes her world, which ends at Chelsea Piers in the south, where she takes gymnastics class..
He was 3 when his parents, hoping to curb his hyperactivity, put him in a gymnastics class.
The older officer had taken a few boxing lessons at a gym not far from where his daughter went to gymnastics class.
After gymnastics class one Saturday morning, when she'd had little breakfast, she slurped down a mash-up of blueberry, pear and purple carrot.
