in bad times, you must.
The time to advertise your physics course it now, colleagues. Counselors are heading out into classes to obtain student schedule requests. If you want to maintain or--better yet--increase your physics enrollment, don't keep your class a secret.
Physics is not (yet) a required course for high school graduation. You and I will likely be happier if it never becomes a required course. But that means nobody really needs to sign up for it. Yet physics is the grooviest course offered at your school, so everyone should be signing up for it.
You could visit the chemistry classes on your campus and do a dog and pony show, begging chem students to sign up for physics. I don't recommend that approach. It shows your willingness to accept the 1950's science pipeline: everyone takes biology, half proceed to chemistry, and half of them proceed to physics. No! Chemistry is not a prerequisite for physics.
In years past, I took the effort to mail out personalized letters to all chemistry students' parents, asking them to encourage their son or daughter to enroll in physics. The success was modest. And it buys in to the 50's enrollment model.
One year, I did something that seemed much less "personal," yet increased my enrollment from four sections to six. A 50% growth rate! How unsustainable is that, Al Bartlett?!
What did I do? I advertised! I used these flyers printed on fluorescent, "neon" paper: paper so bright you can see it in the next county. Astrobrights are nice, but fluorescent, coated paper (one side color, one side white.
The point is to let students know how cool the class is and that you want them to enroll. Sounds simple, but it works.
I would also recommend that if you have an Algebra 2 barricade blocking enrollment to your class, do what you can to remove it. It really doesn't need to be there. You can run a perfectly sound, standards-based physics course without an Algebra 2 prerequisite. Students need Algebra 1, to be sure. Geometry would nice (though not required). But they truly do not need Algebra 2.
Physics classes that sit behind prerequisite barricades of chemistry and Algebra 2 will succeed in keeping most high school students out of the best science course offered at your school: physics! So knock down the barriers. And advertise.
I will personally guarantee your results or double your money back.