How to restrict child's device access times

We have the AT&T U-verse router 5031NV-030.  Sadly, this router doesn't contain features most routers have for over a decade to restrict access times for specific devices. We want to restrict our 10 year old's tablet from accessing the wifi after 9pm on school nights. Sure, we can take the device every night, but most routers allow you to restrict access during certain times automatically. Not this one. We downloaded the AT&T SecurityCenter software, but it only shows devices with the software installed. So no tablet displayed. Does AT&T offer modern functions to accomplish this? Or are there any 3rd party solutions which would accomplish this as well? Thanks!