Setting up your classroom for App Inventor should not be difficult. This page explains what you need to do in advance and what you should let the IT people know to set up at your school.
App Inventor lets you develop applications for Android phones using a web browser and either a connected phone or an on-screen phone emulator. The MIT App Inventor servers store your work and help you keep track of your projects.
You build apps by working with:
Your app appears on the phone step-by-step as you add pieces to it, so you can test your work as you build. If you don't have an Android phone, you can build your apps using the Android emulator, software that runs on your computer and behaves just like the phone.
The App Inventor development environment is supported for Mac OS X, GNU/Linux, and Windows operating systems, and most Android phone models. Applications created with App Inventor can be installed on any Android phone.
Before you can use App Inventor, you need to set up your computer and, for certain cases, install the App Inventor Setup package on your computer. See: App Inventor 2 Setup Instructions.
FIRST, Try setting up and running App Inventor by following the Setup instructions linked from above. If you have any trouble, a list of common problems and solutions are available on the Troubleshooting page.