New Boy by Tracy Chevalier

She noticed him before anyone else. Arriving at his fourth school in six years, diplomat's son Osei Kokote knows he needs an ally if he is to survive his first day - so he's lucky to hit it off with Dee, the most popular girl in school. But one student can't stand to witness this budding relationship: Ian decides to destroy the friendship between the black boy and the golden girl. By the end of the day, the school and its key players - teachers and pupils alike - will never be the same again.