Skype - viewing conversations from blocked contacts

[cakedup]

DS and a boy from his school were speaking on Skype and had a fall out over which online game to play. As a result, the boy verbally abused and swore at DS, and then sent (typed) some abusive messages as well.

The school want to see a record of these conversations but as we deleted this boy from his contacts and blocked him, all conversations have disappeared too.

Is it possible to view typed messages from a contact we have blocked? And is it possible to access phone call conversations?