Todd Campbell, Independence High's principal, said acts of kindness started to spread after someone off-campus was mean to an administrator.
Campbell said the administrator's experience resonated with students, who have been caught being kind so many times the photographs of dozens of teenagers wearing 'Be Nice' T-shirts are displayed on a wall near the school's lobby.
In January, amateur video captured the students' kindness when the Independence High basketball team crowned Daniel Wood, a student born with Down Syndrome, Coming Home King, which is usually reserved for the most popular students.
Campbell says the acts of kindness continue, and not just at Independence High. All 41 schools in the Williamson County district have adopted the philosophy.