I went to the UK with People to People when I was 12. I wouldn't say it was the best experience of my life. I made some friends on the trip, but overall it was a little lonely at that time in my life to be traveling with more or less strangers.
We did raise funds for the trip, and it was a hardship for my family, but I am very grateful that they gave me that opportunity.
As mentioned, the chaperones are teachers, which in my case meant they did an excellent job keeping a tight reign on everyone as far as safety goes. Throughout the training before the trip it was drilled into us that we were ambassadors for our country, state, county, school, etc, and that we needed to act as such. We also met with a Congressional Rep in DC to add further credence to the idea.
I had the unfortunate experience of getting sick on the trip. Though I imagine that was hard on my parents, one of my chaperones took me to the local hospital and stayed with me the entire time. They were also able to notify my parents immediately.
I was able to talk to my parents at a few different junctures, at least once at one of the home-stay opportunities.
If you do allow your son to go, I would coach him ahead of time on how to be comfortable in new situations, with new people, etc. I would also make sure he has a camera he is comfortable using. I'm not sure about the food in Australia, but I lived off snickers bars in England because I hated fish, and that is a lot of what we were served. I eat it now, but didn't then! So getting him ready for expanding his eating experiences would be good!
The views were amazing. The touring was amazing. I would agree that they keep you very busy. It's not like there's every really a moment in the day that you are just sitting around doing nothing.
Overall, it was a great experience. I hope I've given you an inside view to my experiences.