Wear the navy dress with flats or wedge shoes but wear a cami under the dress, so the back isn't see thru. You want a more serious look for a debate. You could wear a contrasting cami that matches your shoes for a pop of color. Lavender, white, or pink would be pretty and not too brash. Or you could wear a cute cardi or blazer with the dress. Good luck in the debate!! : }
the navy dress, wear some nice flats and you are good to go.
school is useless.
I think the first might also be a good idea, you can try adding a blazer on top and see how it looks.