PSA for college students: prerequisites are courses that you must take before enrolling in another course.
There are ALWAYS prereqs. No, you can't get around them or get the instructor to let you in anyway—they know it's more trouble for them if they have to also teach you basic skills you should already have.
Skipping prereqs is not in your best interest. And it's the biggest cause of graduation delay I see as an advisor.
Know your prereqs—or talk to your advisor!