Wireless Internet keeps dropping

Hello,
My wireless network keeps dropping my internet connection. I have made sure the network is at the top of the preferences list, but it still drops the connection every 10-15 minutes. It does not happen on my home network, only the network at school. I have run virus scans and nothing has come up. It is a WPA network with an access code that appears to be working because I can get onto the Internet, I just can't stay on. I am using XP, Intel PRO/Wireless 3954BG on a Sony Vaio TNX15P. Any help would be greatly appreciated.