Cargo prices for schools supplies?? Help.

I have brought it some much needed supplies for the schools (as requested on an earlier thread) with A.A. who give a generous baggage allowance and Sky King(who only charged 95cents for each extra kilo) .. This time Ive bought loads more to bring then discovered the direct British airlines, Thomas Cook and Britannia are charging 8 pounds sterling (about $14) for every extra kilo. Can anyone help? Im disgusted that neither of these will answer any of my emails asking if they will contribute to these poor children by waiving the charges. I'll have to leave all the stuff behind.