Welcome to the forum!
If you are fairly handy with a volt meter, you might begin by chasing voltage. Starting at the "hot" side of the switch, at your brake pedal, will tell you if you even have voltage avaliable.
If you do, mash the pedal, check on the other side if the switch, if you find voltage, the switch is likley good. Move to the back of the bus, check at each light socket, you might find a bad ground at this point, and all that requires is a scraping or sanding, at worse, a new wire.
If you are not comfortable with a volt meter, a test light will work fine, maybe better!
Let us know...and again..
Back to a 5'er after 4 yrs fulltime.
Pulling with a '14 2500 ram, 6.4 Hemi.
Montana High Country 31RE