Wikipedia

http://en.wikipedia.org/wiki/Port_Arthur,_Tasmania
Port Arthur, Tasmania, 2014, ‘Port Arthur, Tasmania’, wiki article, 17 May 2014, accessed 24 May 2014, <http://en.wikipedia.org/wiki/Port_Arthur,_Tasmania>.
I found that this Wikipedia page would be very helpful to a 16yr old reaseaching Port Arthur. It is a medium authority site that contains information about Port Arthur and the penal story - about the prison and convicts such as their punishment, along with other information including pictures and links to get futher information.

Snippit of some of the information on Wikipedia "Port Arthur, Tasmania"

Port Arthur was named after George Arthur, the Lieutenant Governor of Van Diemen's Land. The settlement started as a timber station in 1830, but it is best known for being a penal colony.
From 1833, until 1853, it was the destination for the hardest of convicted British criminals, those who were secondary offenders having re-offended after their arrival in Australia. Rebellious personalities from other convict stations were also sent here, a quite undesirable punishment. In addition Port Arthur had some of the strictest security measures of the British penal system.