Restrictions: they don't work

I work in a residential (boarding) school here in the UK.

Our school has Wi-Fi throughout, and our school network has a content-filter which does a pretty good job of blocking websites that contain inappropriate content for the children.

Many of the students have devices like iPhones and iPads, and they can use school Wi-Fi to access the internet, but their phones all have data plans, so can access the internet that way too.

We attempt to use the restrictions on their devices (found within Screen Time) to stop students using Cellular Data (or Mobile Data as we call it in the UK) but this simply does not work!

For example, you take a student phone, turn Cellular / Mobile Data OFF, then go into the Screen Time --> Restrictions area and set "Cellular / Mobile Data Changes" to "Don't Allow", and ensure Restrictions are ON.

This should mean the student cannot then just toggle Cellular / Mobile Data back on... but guess what... they absolutely can! With a single tap, they can turn this straight back on, giving them direct access to the internet, thus avoiding the school's Content Filter.

I can't quite believe there is such a big hole in the system.

Additional Notes:

• I recognise there is a Parent / Child account system on iOS which may work well for a family based set up, but this cannot be used in our type of environment.
• The idea that we should "make this the parents responsibility" doesn't work, as we have a duty of care to keep young people safe, even if their parents fail to take action.
• Other aspects of the restrictions process don't work, e.g. "Allow 1 more minute" of device time actually seems to allow far more than 1 minute, e.g. 30 minutes.
• While there used to be the option to restrict content by age (e.g. 12 and over, 15 and over) this seems to have been replaced in iOS16 with a blanket "allow all movies" or "do not allow any movies" option.

I'd really like help to solve this. At present, it appears Apple have a coherent system to help parents and carers keep their children safe while using Apple products, but in practice it turns out the system has gaping holes and it only gives the illusion that children are being kept safe.