Alas your approach is flawed. Many activities will give away demographics about an individual without it haven't to be expressly stated in the demographics portion of their application. Three notable examples would be...
- Any religious based group like Fellowship of Christian Athletes, Muslim Student Association, etc. - reveals religion
- Groups for LGBTQ+ people - reveals your non-heterosexual sexuality or that you're transgender
- Any gender specific group reveals gender
- Black Student Association, Native American Student Association, etc. - reveals race
- Republican or Democrat student groups - reveals political affiliation
- Any sport labeled men's/women's, or ones that are 99.99% one gender like football - reveals your either a boy or a girl (or transgender depending on state)
- ROTC/JROTC - reveals that you likely support the armed forces, which allows people who are anti-armed forces to potentially discriminate against these applicants.
- School attended - This is important to know because an A+ at an easy school means a hell of a lot less than an A+ at a prestigious school, so can't be eliminated in a meritocracy. Doesn't entirely eliminate one's gender unless they went to an all-boys or all-girls school. And doesn't entirely eliminate race, but the race demographics are out there for schools and if you went to a school that's almost exclusively white (like most private schools) or black (like inner city schools), for two examples, then chances are pretty high you can successfully guess the race of the student just from what school they went to. Does reveal the general area where one lives though. And can very likely reveal someone's financial situation, which can be used to discriminate.
- Commuter Student Association (when applying for graduate school) - reveals location.
And you can't just eliminate extracurriculars because they are a very important part of the application process, especially if a person has an elected/appointed position within the group.
And then there are academic programs that almost exclusively attract people of one gender, like shop and beauty classes, for examples off the top of my head. Obviously not exclusive to boys and girls, but the likelihood of finding a girl in a shop class or a boy in a beauty class are pretty miniscule.
And there are scholarship programs that are linked to minorities - gender and/or race - or regions/states/localities.