Setup complete school environment

I am having trouble setting up a school with management of computers and phones...

Right now we are having about 40 windows 8 and 7 computers with only an admin account with password, an ESXi server with synology DSM, LDAP database with all students and teachers and a game server (For breaks)

I was talking to the principle about getting a Windows server and professional editions for computers so we can get an AD and other management stuff, but the problem is that he won't use money on that kind of stuff.

So i was thinking about changing all the computers to Linux, the problem with this is that nobody ever has used Linux before, but that is not their decision.

So does anybody know to get something like a complete Windows environment with management and all, but with Linux instead...

This is a list of some stuff that almost is requirements but not really if it cannot work:

• Free
• Easy to administrate
• Management of all computers (Asset management, software lists, deployment of new stuff, etc.)

Update: I am trying to deploy Zentyal and OCS on our server...