why does becky leave school

Becky is leaving school in order to take a post as a governess at the Crawley Estate.

Becky is enrolled at Miss Pinkerton's academy. She will pay for her schooling by teaching French. When Miss Pinkerton tries to get her to also teach music, Becky rebels and demands that Miss Pinkerton find her a position as a governess.

Rather angry, Becky leaves school at the same time as her friend Amelia Sedley.