Question : Recommendations for VoIP.

I know very little about VoIP.  I am looking for a recommendation or two about designing a system for a small school that I work for.  When I say small, we are talking about max 10 classrooms.  Each room has a wired internet connection, that leads back to a linksys WRT54G wireless router, and linksys 24 port switch.  The wireless connection reaches only so far as the room it is in, and the rooms adjacent to that room.  The classrooms themselves all have ethernet cables running through the walls.  What they dont have ironically, is phone cables running through the walls.  Thus, the classrooms have internet, but no phone.

Here are the main features I am hoping we can get with a VoIP.

01.   Intercom.  The ability for classroom A to page someone in classrooom B.  The ability for A to page all phones in the building would also be magnifico.
02.   Ability to call out would also be a nice feature, but strange as it sounds, is the least valueable feature for us.
03.   Each classroom have their own phone number.  Not even necessarily their own phone number, but a way for incoming calls to be routed to individual classrooms.  Even if for instance, someone were to call the main number, the secretary were to pick up, and then be able to transfer the call to the classroom, would be good enough.  So, that or their own numbers.
04.    Individual voice mails.  Probably the greatest feature would be the ability for parents to leave a voice mail for the classroom teachers.
05.    Other phone features like Caller ID, three way call also a plus, but not a must.

This is not a rich school, as you can probably tell from the lack of telephones in the classrooms problem I'm trying to deal with.  I honestly dont know what kind of budget they have for this kind of project.  Anyhow, any information that our Experts have on this subject would be much appreciated.  Thanks.

Answer : Recommendations for VoIP.

try
http://www.3cx.com  phone system the commercial edition is not that expensive.

or you can go with a hosted solution like
http://www.accesspointinc.com/voicepointFLEX.htm
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