iPod touch Why safari doesn't work in school??

Probably because the interface between the wireless abilities of the Touch and the wireless provided by the school is different.
I had the same problem wondering what happened when 2.00 released for the PSP. It would let me get as far as the login screen when I tried to access the internet, but on my PSP, it would keep rejecting my username and password.

There's a Mac lab at our school though, for the Journalism class, and I can connect to that 🙂

It is relatively easy for anyone with control of the wireless routers to set them so only certain PCs that connect through it can get to the internet. So for example if I was in charge of the school's routers, I would set them to recognize the school PC's specific mac addresses and exclude everything else. That would keep people with wifi enabled PDAs, iPod Touches, strangers with wireless laptop in the parking lot, etc., from using the internet access intended only for the school's use. This works even if you know the password for the wifi.

If you want access to the school's network, it is reasonable to find the network administrator and ask their permission. If they give it, they will also add your Touch's mac address to their router and you'll be able to find the internet.

Hope that helps.
4D

There could also be problems with the way that the network is encoded.

Is it WPA encrypted or unsecured?

WPA enterprise is not (AFAIK) supported on the iPod touch/iPhone yet, so you will not be able to connect. Normally on a laptop or supported device you download the certificate and connect via e-mail/user and password.

However if it is unsecured it is more likely to be MAC address controlled as someone has said.