My recommendation for your household is Circle, or a similar wireless router device. Circle enables you, through a phone app, to control electronic devices connected to the family network. You can set up time limits for each school ipad (i.e. off at 7PM), as well as amount of time on device, and what, if any websites (Youtube) can be accessed. You can put a limit, say 30 minutes for Minecraft and 20 minutes for Youtube. You also have a control button, which you can use from your phone app, to shut off all wireless in the house. My kids hated it at first, trying to unplug it (you get a message it was unplugged, then Internet shuts off) and just go over to friends’ houses with unlimited Internet. You can set it up so that certain websites are off limits, say after 6 PM. You can also setup unlimited time for weebly or Google Classroom, so they always have access to school sites.
Additionally, I completely agree (and disagree with the stupid school administrator that said computer work is the future) that computers in the hands of all these kids for the purported use of school work is a DISASTER. Complete waste of time and money for school districts always crying poor. Parents get no work sent home and it is difficult to see where and at what level your child is at, and what they are working on. More difficult for parents to be involved in the education of their children (which I think is purposely done). Get your childrens’ passwords now and have them walk you through the sites the teachers are using. Know their accounts and passwords and monitor them.