Thats crazy. Thank goodness for being thorough and reading all the print.
One thing that is important to note is that most people when they adopt fitness into their life, keep it for most of it. For those who really enjoy it or at least enjoy the benefits, its an easy thing to hang on to.
The other part to this is that its a giant learning experience of techniques, diet, exercises, training frequency etc.. the catch is that they are all individual. Each person, regardless of what template they use will all learn over the the differences they each require to make progress, to learn what exercises they will learn are the better.
My introduction to fitness was as a teenager as well, and I have made tons of adjustments, added and subtracted exercises and just recently found a new training frequency that lets my body respond really well - which was completely different than 8 years ago.
My advice to you is considering introducing them to a weight training facility, perhaps at school or a local gym and then seeing you can find someone to instruct on proper execution. Training when young is more about quality nutrition and enough stimulation(not annihilation) of the body to produce results and keep it fun and interesting.
If there is something I can do for you - please let me know. You can direct questions directly to me with this link http://www.justanswer.com/general/expert-cscsmike/
- I believe I am the only fitness and strength specialist on JustAnswer.