As far as I am aware, a Disclosure document only needs to be signed if the applicant requires airside access on a permanent photo i.d. and operating airside as part of employment. The criminal record check that I am aware of is specifically aimed at those working with children and vulnerable adults. I am not sure if student pilots fall into the category of vulnerable adults, but some could be considered to be children if they are learning to fly whilst under the age of consent.
I guess.....
Mind you, I am no lawyer!
Cheers