As with any educational program, there are mixed results. Some years your kid gets an amazing teacher, has an incredible class that gels. Other years, results are not as wonderful. As at camp, there are great counselors, great heads of program, and the other kids in the cabin are dedicated to speaking the language. Other years, less optimal.
My girls went to perhaps 10 years of sessions of Japanese and then French camp. They remember no Japanese from the early years, but had fun. French was an incredible experience most of the time and their French was very good as a result.