If it were me and I have to admit looking at this through UK eyes this situation requires quiet dignity, not only for yourself, but for your students too. So, for what it is worth, I would go steady on the crimson. How about white blazer, white(very, very pale blue is worth a thought), black trousers and well shone black shoes. To get the school colours into the equation a regimental style tie with a crimson stripe----or a plain crimson tie as a second choice. Sometimes to make a point, silence and quiet dignity can be deafening!
I couldn't agree more and might even suggest going even more "quietly" substituting the black trousers for some good quality grey flannels as the black trousers with white jacket suggests dinner wear on a cruise or Bertie Wooster on holiday in Cannes (sans Jeeves).