Just a question

You need to get permission from the network administrator to ''plug in'' a Wireless Access Point (WAP).

Once you have a WAP (with the security settings your network administrator recommends), any computer that is to make a wireless connection to the WAP will need a Wireless Network Adapter.

The Wireless Network Adapter needs to be compatible with the WAP's broadcast standard (wireless-g, wireless-b, wireless-a).

Cheapest WAPs are often Wireless Routers that can be configured to function as a WAP.

It can be difficult to find a WAP that is simply plug-n-play because the existing network setup might not match the default WAP settings.

I have used small wireless routers as WAPs for classrom and hotel use. They are usually called travel routers or compact routers. You plug it in, configure it once, and pop it into your notebook travel bag when you are finished.

I have had success with the following compact/travel models:
Linksys WRT54GC
Linksys WTR54G
Netgear WGR101

I usually travel with Linksys WRT54GC because it has a lot of functions and extra ports if needed.

You could cause a lot of problems on your school networks that would upset any network admin. Believe me, it's easy to track too. But, if you got permission to do this, the setup is simple. Purchase ACCESS POINT and hook it into the port in the wall. Broadcast your signal and voila! Most of the time, this will not work because the Access Point needs to be registered on the network that is running on. Chances are you will be able to connect to the network, but internet might not be allowed. (Depends on the schools network.)