My group aren't learning their lines for drama

Okay so basically, we got our drama script last month, and we blocked each scene before half term. My group still do not know their lines and its so annoying. Obviously the examiner marks us separately however i feel as though its much harder to do well if the rest of your group are not bothering at all.

3/6 don't know there lines granted one person has the longest part however its been a month and they act as if they don't even try. I told my friends about this, and he tells me that im saying "shxt" which isn't true considering he literally doesnt know scene after scene

Our exam is in 17 days and i feel like only three people are actually bothering to make an effort whereas the others can't be bothered to rehearse or meet up after school.

What should i do about this?