Parental controls on Amazon Fire tablets

[enjay]

We've bought some Amazon Fire tablets (the new ones, with Alexa) for shared use among some students. I'm trying to set up the controls so the students can only access apps which I approve. I have done the obvious of setting up a household, creating a child profile and so forth but I can't see how to restrict the native apps - I have found the setting to control which downloaded apps my "child" can open, but that's it; I don't want the students to be able to do much other than open the browser, a couple of chosen apps (not yet installed) and use the camera.

 

Where am I going wrong?