I fly from a mountain site which is primarily ridge soaring. Standard
height for two of the three nearby mountains is 2000 feet. One more
distant mountain requires a 4000 foot tow to allow sufficient
altitude to return to the field with a good safety margin if it turns
out that the lift isn't there. Usually if a student is in very early
training and unable to safely soar the ridge the instructor will climb
one or two thousand feet on the ridge, move away from the ridge, let
the student fly various maneuvers and then, when back down to
1700-1800 will climb back up on the ridge. repeat as necessary. If
there is no lift then higher tows are taken. We normally take 3000
foot tows for the purpose of a season check flight or if spins are to
be performed on a day with no lift. The students are usually able to
handle the ridge soaring quite early in training.