The first thing we tell new guys is to tap if there is any doubt.
As to letting them work subs on you, either have an experienced person watching or make sure the new guy knows what a tap means. FYI, in our gym we teach to either tap, snap your fingers, or say 'tap', as there are times you cannot tap out with your hands (like a double armbar).
When given the choice between big business and big government, choose big business. Big business never threw millions of people into gas chambers, but big government did.
"It does not take a majority to prevail, but rather an irate, tireless minority, keen on setting brushfires of freedom in the minds of men" -Samuel Adams