Grounded from their cell phone. Does an App exists like this...

We just took our son's cell phone away for bad grades. I was wondering anyone knew if there is an app that turns a cell phone into just a phone and is password protected by the parents or guardians? I would like to still be able to contact my child, and have them be able to contact me, in an emergency. I did some Googling, but I didn't find an app specifically geared towards this situation. I see that, for whatever reason, there are apps to turn your "smart" phone into a "dumb" phone. These wouldn't serve my purpose because they aren't password set to stay "dumb". Figured I would throw this out there and see if anyone knew of an app like this.

​

EDIT : It's an android phone.