Harry Potter And The Prisoner Of Azkaban -

Harry discovers that Sirius was his father’s best friend and is actually innocent.

Sirius Black, a notorious mass murderer, escapes the wizarding prison, Azkaban. Harry Potter and the Prisoner of Azkaban

This was the first film where students wore "muggle clothes" like hoodies and jeans instead of always being in robes. Harry discovers that Sirius was his father’s best