Lenses for documentary style portraits.

[TDshoots]

I'm about to begin a project in my highschool that is exploring the diversity of the different social groups in the school, I'm looking for a lens that will do well indoors and will capture the scene around the person, as well as the person, I'm shooting with a sony a55 so I need something compatible, something of the highest quality, I NEED sharpness and color accuracy, I'm thinking Zeiss possibly, any suggestions are welcome.

Thanks,

Tom.