It won't block sites -- I'm not sure there is an Android app that can do that -- but I would nevertheless highly recommend
Screen Time Parental Control. It will let you impose daily time limits, bedtime hours, school hours, and you can block whatever app you want during school, bedtime, or whenever. It also gives you a detailed real time summary of what your child is and has been doing on her device -- what app she is using, what website she is viewing, and every search term used. It is wildly authoritarian in the control one can impose, but I find it absolutely necessary for my two tweens, one of whom has both a phone and a tablet (the other one just a tablet). You can also use it with
a separate remote control app on your own device to monitor, control, and authorize usage of the device, apps, etc. (as opposed to going to the website or child's device to do it), but it's $3 a month for a subscription (there's a 7 day free trial). I've found it's worth it.