BTW If you want me to give a talk at your school, feel free to email me at the address think (AT) royalinstitutephilosophy.org (easy to get address wrong - note no "of" between "institute" and "philosophy").
Obvious subjects would be A Level Philosophy and RS topics, or any subject relating to my books and/or research. Younger kids too (e.g. on my Really, Really Big Questions).
(P.S. I do usually charge a fee, though not for most deserving cases e.g. comprehensive in a deprived area)