Here are some resources to help you get the feel of the culture of a private Japanese school. Some are a bit exaggerated, but that is okay in a roleplay setting based on anime (anime tends to be very exaggerated).

Top Suggestions:
Hana Yori Dango
Ouran Host Club (fandub)
Ouran subtitled

Other Video Recommendations:
Hana Kimi
Gokusen
Sailor Moon Live

Resources:
Japanese Education Wiki