NOLS typically has the students trek out at the end of the course on their own. Back when I took the course, not only did we have to backpack through 50 miles of rough terrain in four days, we also had to do it without food. Ungh.
The idea is to make you apply what you have learned. I believe NOLS has since stopped the policy of not having food the last four days. But I can't agree with their policy of having teenagers in a group in the wilderness without at least one adult with them. They should have had a mixed group by age - I was one of four students under 18 in my group of 14, and there were some college-age students, but there were also adults in their twenties and early thirties so there was never a teen-only group.
I kinda agree with you but what would the adult have done?
The kids should have been walking in a tight line and waited in a group on the other side of the creek before moving on.
Instead the lead kid went out of sight so the bear saw 1 or 2 people instead of a group of 7 which may have made it think twice about charging.
Other than that I don’t see how an adult would have helped.