stay longer in a class

[arzgol]

What do you say in English when something takes more time than we expect? We say overdue, overload,. and so on.

Could you please say the below sentence in another way?

She had to stay longer in the class because the duration of her biology class was more than two hours.


Thank you for your response.

[English Freak]

You could simply say:
She had to stay on because her biology class took more than 2 hours.