This was promised back in 2010
https://www.theguardian.com/society/2010/dec/15/mixed-sex-hospital-ward-fines
Governments have been struggling for 15 years to end the sharing of wards by men and women. Lansley said in August that it would end in all but accident and emergency and intensive care units by the end of this year.
The only reason mixed wards happen is because demand has grown but funding has not. The NHS is being crippled on multiple fronts by chronic lack of resources.
That we're reading this educational policy change in the newspapers and not from a professional teaching group tells you that this is simply a political manoeuvre.
These kids are already watching porn on their phones, you aren't protecting them from anything by refusing to teach.