Nine-year-old Celeste Marchant just wants to do "flipz n trix" with the boys.
But a New Zealand gymnastics club says instead she has to do "twist n turn" with the girls.
Bridget Marchant said when her daughter Celeste asked if she could join her friends' Gymnastics Nelson class, she looked on the website and found it was advertised for boys.
She emailed the gym asking if she could still enrol Celeste, as "she is equal to all the boys and her best friends (who are boys) go to this class".
However, Gymnastics Nelson centre co-ordinator Debbie Shaw said she'd need to join the girls' equivalent class.
Shaw said the classes were structured based on feedback from both participants and coaches.
"The boys, for 'flipz n trix', tend to do more free running," Shaw said. "The girls [for 'twist n turn'] tend to like to do some of that and then also some bar and some beam, and that's the coaches' feedback."
Marchant said Celeste wanted to do gymnastics with her friends and didn't think they'd been given a reasonable explanation about why she could not join.
"Really the only reason I can think of is she's a girl ... I just hate the way that would have made her feel and the message that's giving her, it's not good."
While she hadn't looked at the specifics of the class structure, it seemed "a bit weird" that an exception couldn't be made.
Celeste had no interest in the beam and bar work and was keen on the other class.
"She wants to do flips and tricks, that appeals to her," Marchant said. "[The gym staff] did say she'd be on the floor at the same time as her friends, but I thought, imagine that for her, she'll [have to say] 'I'm over here [because] I'm not allowed to be over there …'"
She said Celeste had seemed upset when she'd been told about the gym's decision.
"She wasn't crying or anything but I think it just further accentuates what she sees all the time, when she's trying to run about with her mates ... I think she considers herself not quite equal ... as a girl you're just a little bit down the rung so she has to work harder," Marchant said.
"When she was a little kid I made her a book of 'girls doing awesome sports things', just so she can see that imagery."
Shaw said the club offered other mixed-sex classes and had holiday programmes where both boys and girls participated together, but there wasn't a mixed "flipz n trix" coaching option. She said all children did warm up together.
Shaw said the club had a format that worked and when she'd asked the coaches about Celeste's request, they thought it would be "very, very difficult" to include her in the boys' class. The coaching staff had run a mixed "flipz n trix" classes previously without success.
"We found the boys requirements different for this age group to the girls, and we could not safely combine them successfully."
Shaw said customer demand was that girls use some different apparatus during this class, such as the beam and the bar, while the boys' focus was more on the floor, tramp, and walls.
They had two groups of each sex, with eight children in each, coached on the floor at the same time and when the gym did run mixed classes as part of the holiday programme, the children still tended to separate themselves out into boys and girls.
Shaw said classes were always fully booked with waiting lists, so "the recipe is working" in terms of format.
"It's got to be something that works for the coach and the public, for health and safety and for comfort of the people. We've got girls who don't want to be particularly working with boys, and then you're going to have some that do."