Unpaid internship : biggest sin!

I did an unpaid internship but we didn't do any work they got paid for either. My internship was basically a school but in a work environment and where you actually learn things and the things you want to learn.

Every day we had a few presentations on subjects and some homework. And we did work on projects but it was done fully by interns. From PO role to devs as testers. We had to set it up and everything. Sounds like hell, but was the best thing I've had.
They also gave a job guarantee 2 months in. So I was working there before my school ended and they were actually involved in improving our school for us. I now see that company as family.

Sadly, unpaid internships are the norm where I live and most schools require that students spend at least 3 months in an internship.

If it's not your first internship, then I agree. If it's your first experience, then the company is probably doing you a favor by teaching you how the world works. It's really a stage of school. But of course it all depends on what you're doing.