Secondary school teachers and mobile phone policy

[DisposableNN]

If you are a secondary school teacher what is your schools policy re your personal mobile phones during the school day? Are you allowed to use them to contact a parent?

My D's teacher called me yesterday from her personal number to inform that D's had received a behaviour point. She had already emailed me (no problem with that) and i had responded. Why not call me from the school number? Why use her personal number? I know its her personal number because I can now see her and her family on WhatsApp.
Is this OK?

We are absolutely not permitted to call parents from personal moble phones.

Thank you Harry I have no problem with school contacting me re behaviour but it didn't feel right that it was done from the teachers personal phone.