What is the name of that series where three school teens & principal fight and capture aliens?

my sister used to watch a show with three teens (blond curly haired girl, white boy, black boy with glasses) and a black school principal/teacher used to fight and capture aliens to save the world... there was something about a portal, they used to communicate with watches... I just can't remember the name of the show... does anyone know that show? I don't remember if it was disney xd, or nick, or I just can't remember...
Asked Jun 16, 2011
the troop, and its on nick
Answered Jun 17, 2011
thanks :)

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