Say “no” to learning opportunities when the effort can not be counted as deliberate practice hours of some kind. This means the parent stays alert to changing conditions so that his child can gracefully bow out of what previously may have been helpful, but no longer is.
In one situation, for example, my 12 year old son spent time cultivating a relationship with an older gentleman who had a lot of talent in a specialized area that he was eager to pass on to a younger person. As a consequence, I encouraged my son to read up on some topics and buy some protective gear that this same man had recommended so he could let him wield some torch bearing equipment. However, as the months rolled by, this same gentleman started showing a growing lack of confidence in his own abilities due to his increasing old age. I stepped in and helped my son bow out of such teaching sessions.
My experience has been that if there is someone whom you think your son or daughter would benefit from their teaching, but for some inexplicable reason your younger teenage is not wanting to be around that person, it is probably because the adult no longer has the social skills necessary to be helpful. If your child is an otherwise respectful child, then the problem is probably not with your child. We all know that some adults behave very differently around young people than when they interact with you as the adult. But it is not up to your child to have to have to explain the subtle differences to you. It is your job to be on the alert and help your child find a way to gracefully bow out.