I have not been able to find one from over three years of looking. Stonewall have a list but won’t publish it anymore to protect their supporters from scrutiny.
My daughter’s now ex-secondary school wasn’t listed as a Stonewall school but uses a lot of observably Stonewall content such as language definitions, supported by local Stonewall clone charities. This was not made clear or published on their public or intranet sites, I only found out by digging and digging.
If you read a school’s published policies related to equality, bullying, mental health/wellbeing (particularly in the child focused sections), RSE, PSHE and you see language that asserts a use of language you don’t feel comfortable with, promotes external third parties or references actions the school will carry out or decisions they will make without qualified and regulated staff then it’s a Stonewall school in practical terms.
I’d recommend comparing GMC guidelines on Gillick communications and decision making against any Gillick or Fraser guidelines that show up directly in the school polices or as a reference to external operators to get an indication of the school’s support and status for your parental responsibility. Gillick is frequently used to evade parental responsibility, it’s a formal assessment that needs to be carried out by a registered HCP for a specific purpose.
I also found out that the local authority is a Stonewall schools champion or whatever, this is where the deluge of policy is poured into the all the local schools. It took an FOI request to find that out.
In summary the “Stonewall culture” is too furtive for trust to exist, this includes the lack of transparency on who’s paid up to make use of their services. I have to recommend keeping any child away from an organisation where this operates.
I hope your research into other schools is more positive for your family.