The Fourth(2008)

Overview:

A thriller about the dark and dangerous secrets shared by a 12 year old boy, his new teacher and the school principal, a catholic priest. Months after the death of his father, Simon (12) discovers the affair his Mother (Sarah) is having with a charming but enigmatic new teacher (Mario). The boy discovers the teacher's intentions and his dark secrets, but with his mother in love, it seems there is nothing he can do to show her that their lives are in danger.