Club 15 was a construct of The Campbell Soup Company. Club 15 was an "exercise club" for teenage girls. A former olympic gymnast and coach, Muriel Davis Grossfeld was contracted through a New York advertising firm, BBD&O to travel the country visiting schools and teach exercises to teenage girls.
I think the album was made in 1968 or 69 or shortly after Muriel did coaching chores for the U.S. Women's Gymnastics Team came back from Mexico City. Read more here.