I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this is happening.
Making up untrue statements of fact and spreading them to destroy a person's reputation is defamation of character. When a statement goes to someone's chastity or accuses them of committing a crime, reputational harm will be presumed. Calling someone a prostitute qualifies under both of those categories. Once you establish that statements were made, the judge will assume your reputation suffered without you having to bring in additional witnesses to prove it.
Since they're essentially costing you the money you spent on your classes, you can request that they be ordered to reimburse you those amounts. If you can prove that they stopped you from getting a job by making up lies about you, you can ask the judge to order them to pay you the salary you would have gotten but for their malicious and unacceptable behavior.
Each of the students who repeated these things about you can be sued as part of the same lawsuit. And you can also request punitive damages, which means the judge will look at the things they said and decide how much they should have to pay.
A lawyer isn't required here, and unless any of these students has significant assets, it may be hard to find someone to take the case. But you can seek up to $25,000 in Small Claims. Small claims is designed so people can represent themselves - your local court should have forms to open the case. You can sue them all together. And a judgment is good for years, so you have plenty of time to recover even if they're not making a lot of money now.
If you have any questions or concerns about my response, please reply WITHOUT RATING. It's important that you are 100% satisfied with my courtesy and professionalism. Otherwise, please rate my service positively so I am paid for the time I spend answering questions. If you are on a mobile device, you may need to scroll to the right. There is no charge for follow-up questions. Thank you.