My kid's school uses an app called ClassDojo to manage intra-school communication and light social features. Teachers and staff post school-wide announcements and photos to share, teachers post messages to the parents of their students, and parents can communicate directly with their children's teachers. It’s pretty useful and, to the benefit of underfunded school systems everywhere, it’s free to use. But a crucial fact remains that my wife and I don't choose to use ClassDojo. We feel compelled to use this app because it is what the teacher uses, what the principal uses, and we would feel distantly out of the loop should decide to abandon it.
Why the heck would I mention that? Because ClassDojo utterly abuses their captive audience by frequently attempting to upsell parents on out-of-school features, paid access to "memories" from prior school years, and other premium features. I'm not interested in any of that stuff! But I can't ignore the app if I also want an effective line of communication between my house and my kids' school. This is dirty pool in my opinion.