Making mixed sex sport the only option at primary school discriminates against girls. Whether we like it or not, male advantage is real and there is no stage in life when it is not significant. Anecdotal evidence doesn't change this.
This is one of the studies showing this:
https://www.researchgate.net/publication/224914505_Physical_Fitness_Differences_Between_Prepubescent_Boys_and_Girls
Excerpt:
The physical fitness assessment employed sets of aerobic fitness, strength, flexibility, speed, agility, and balance. The boys presented higher values in all selected tests, except tests of balance and flexibility, in which girls scored better.
The vast majority of sports reward the qualities boys excel in rather than those that girls do.
This graphic sets out the difference in achievement clearly.
https://twitter.com/sharrond62/status/1620808961367629828/photo/1
And here's one just for 8-year-olds:
https://twitter.com/sharrond62/status/1620501818777411584/photo/1
There is no reason why separate boys and girls sport sessions should inevitably lead to the concept of girls' sports (netball) and boys' sports (everything else). Schools can decide which sports to offer and then schedule boys and girls sessions in those sports. In a small rural population, mixed sex sessions may be unavoidable especially for team sport, but in that case there should be equal numbers of boys on each team as far as possible.
If girls have to compete in individual sports with boys, then results should be recorded and celebrated separately - fastest girl, fastest boy, etc. Boys need to learn to respect the athletic achievements of girls as a distinct class - as do girls for themselves. Pretending that boys and girls are the same when it comes to sport just hurts girls. They're not the same.
In primary school, the emphasis of sport is supposed to be on fun. How much fun do you suppose was had by the girls on OP's DD's team? Whether the sport is netball or football, some of the boys will bully or ignore the girls. They're just ordinary girls who like netball, not world-beaters in the making. We're trying to get these kids to enjoy running around and getting sweaty, to learn about cooperation and competition, build resilience and confidence - and to taste a measure of success. If a young girl's experience of PE is either being desperate to join in and being ignored, or having to tussle with someone who is much stronger or much rougher than she is used to, she may well drift away, because it's no fun any more.
The England Lionesses' letter to the Government last summer has this paragraph:
We ask you and your government to ensure that all girls have access to a minimum of 2 hours a week PE. Not only should we be offering football to all girls, we also need to invest in and support female PE teachers too. Their role is crucial and we need to give them the resources to provide girls' football sessions. They are key role models from which so many young girls can flourish.
Full text:
https://twitter.com/Lionesses/status/1554829482757828617?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1554829482757828617%7Ctwgr%5E0ab0d8ac2dc0810e01c47df9cd097544cb62b64c%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fwww.itv.com%2Fnews%2F2022-08-03%2Flionesses-write-open-letter-to-allow-all-girls-to-play-football-at-school
Leah Williamson (captain of England Women) has said:
Q: Tell us about a coach that has particularly inspired you.
A: ...All of my coaches were incredible along the way. I could have had a terrible experience playing for a boys' team aged six but my first coach made sure it was a experience I want to relive over and over!
Full article here:
https://www.arsenal.com/news/leah-williamson-shares-her-inspirations
And in the same series of articles, here is Lotte Wubben-Moy (driving force behind the letter):
Q: Looking back, has there been a coach that particularly inspired you?
A: Back in primary school, my P. E. teacher Paul was someone who gave young girls a space where they could feel safe and feel like they could be themselves. He helped me start a football team at my primary school, a girls' football team, when there wasn't one and that really set me on this path.
Full article:
https://www.arsenal.com/news/lotte-wubben-moy-her-inspirations-and-ambitions
She has also said that the letter was sent for the sake of the girls who boys won't pass the ball to, as much as for budding Lionesses.
Would you be happy for 11- and 12-year-old boys to compete routinely against 14- and 15-year-olds? Because it's the same thing. It would destroy their confidence.