OurPact is a parental control app that allows parents to limit screen time and app access on Andriod and iOS devices. It is available in both Free and Paid versions.
It allows you to setup a schedule, so their phone becomes loses internet and app access at their bedtimes. Because it can be set up on a weekly schedule, weekends can have later times then school nights. You can also block or access manually as the need arises.
The Parent App, as seen in the picture below, allows you to create times the phone cannot be used. You can note the activity, time, and day of the week. The event can then be toggled on and off as needed, for school breaks and summer vacations. You can also override all of the schedules with a manual override.