The school ipads are for student to use to access the curriculum. When considering an app consider how it connects to your curriculum. Is it a forced connection or authentic. Does it actually connect to what you want the students to know/be?
Apps that over more than one type of activity are preferred, but not required.
Creation apps are encouraged.
Skill/Drill apps are also discouraged.
Consumption apps are discouraged.
You may absolutely have apps that are specific only to your grade but we would like to know if other grades could benefit.
The integrationists can help you do this. They have an iPad that they can download the app/s onto for testing, which you can borrow.
Even in grades 4 and 5 we will not install apps that are 9+.
The ratings are made by Apple and we have no control over how an app is rated.
Apps that rely on this should not be considered as in-app purchases are not allowed with managed iPads.
Some of these apps do have a full paid "education" version so it is worth a bit of research if you really like the app.