Re: Summer camp for a 15 years old
Here and back to Australia for just one week, that would seem to be difficult, will take a few days to get over jet lag then a day or more to transfer to camp once in CH.
Your biggest problem will be timing...most everything will be on offer for the summer holidays, but this does not include September and likely not June as well, as most CH and europeans are in school then.
Language schools often have summer camps so that may be of interest. Best to google summer camps switzerland, and you will find a lot, most have many activities, including hiking. However, most that I know of are in the Valais, so that may be too far for you.