Mr Teacher, I suggest you might be able to arrange for a visit to Wittering or Cottesmore. Find out the station telephone number, call the PA to the Station Commander and explain that you want to write to him regarding a possible school visit. Ask for his name so that you can personalise the letter - it could make the difference... It will probably be passed to the Community Relations Officer.
You might even get a chance in the flight simulator (it's at Wittering.