A school that is (or wants to be) a "big name" at SMC or BOA probably won't look at you. A school without those aspirations will be more likely to at least look at your resume. It's certainly not impossible.
I would consider talking to the high school you feed, see if they will have an opening or know someone who will. A personal recommendation goes a LONG way.
Also consider getting involved with an indoor drumline, winterguard group, indoor winds, or DCI. Anything to get a foot in the door and some experience with marching.
If you're a woodwind player, often it's expected that you will teach (or at least manage while a tech does the teaching) the colorguard. Be prepared for that.
It's definitely possible to be a great high school teacher with minimal marching experience. You'll learn as you go. There are very few high school jobs that don't involve a lot of responsibility with the marching band.