Screen time down time is easy to overcome by changing phone’s time. I use screentime To control my daughter’s usage of her iPhone. Is there a way to forbid her from changing her phone clock time?

Have you disabled her permission to make account changes in the Screen Time restrictions? That is the only restriction I can think of.

To be honest you will have an uphill struggle to control it with intelligent resourceful children.

OK here is a resource I found but cannot test.Try it

https://www.thetechmum.com/2021/07/28/simple-steps-to-stop-your-kids-from-hacking-screen-time/

Great!

I can't take credit for the author's research but I have stolen some of it!