Game freezes, and continues (depending on wifi)

Every time I play League at my high school, it freezes randomly, ranging about 2 - 15 times per game. This problem does not occur when I play League in other places. The school login is required when the computer is first connected to the wifi, and seldom disconnects itself, but this was not the problem. I was still connected to the wifi, but it freezes by itself. This problem also frequently occurs on my friend's computers, and we have no idea how to prevent it from ruining our games.

Since I play on a Mac (OS X 10.8.5), whenever it freezes, I force-quit League and reconnect every time. Whenever I play too, I make sure that no other application is running other than League, and my Firewall turned off. I do not block any cookies from the Preference Settings from Safari, and I did not make any changes to my IP Address or DNS servers.

Is there any application that I can use or settings that I can change to fix this problem? Thanks,