It's good to mentor students.
Anna had been working as a teacher for a while, and she wanted to be promoted soon.
Anna wants to do something that will impress her boss.
Anna starts mentoring students by spending time with them after school to impress the boss.
Anna enrolls in classes, so she can further her education to impress the boss, so she must leave right after class each day.
Anna's students all do very well and benefit from the extra time with Anna.
Anna cannot spend time mentoring students after class and a few of her students really fall behind.