Patrick Vera wrote:

Does anyone know which (if any) of the Ranma cast would have been at
school at the same time as Kasumi? Are there any experts on teh Japanese
school system who could hazard a guess at which classes Kasumi might
have taken?

Nope, no one introduced in the manga, to my knowledge
is Kasumi's contemporary as far as school goes.

Nabiki and Tatewaki would have been first-year students when Kasumi was
in her final year.  

-- David