create private Google Play channels. In a private Google Play channel you can restrict distribution of apps to just the people within your domain. It's important to note that this only works for apps that are developed by people within the domain. You cannot use it to push 3rd party apps to users of your domain. Google Apps domain administrators can find directions for creating a private Google Play channel here.
Applications for Education
If students in your school are developing Android apps using the MIT App Inventor, distributing those apps through a private channel could be a good way for students to get feedback from teachers and students within your domain. If you would like to learn more about the MIT App Inventor please read my post about it here.