How long is the lesson for? She needs to look at the QCA site to see what the objectives are in the lesson, (hitting AT1 and 2 as well)and also if she can get hold of the syllabus (written by the SACRE for the LEA), that'll help as well.
Year 8 - I wouldn't make it too complicated.
Starter: What famous religious figures can you name? (might get Buddha, Muhammed, Guru Nanak, Abraham and hopefully JC). What do these figures have in common? (hopefully answer - they all are 'founders' of a religion).
Then, Christians think that JC is extremely 'special' - why - you'll get various responses.
Then, put JC in historical context - we know he exists as mentioned in Josephus - but what made him special, why did people then, and now think he was the son of God?
You may then get answers about miracles (need to define what one is perhaps), parables, teachings, actions, idea of sacrifice, resurrection. Put these in columns on the board.
Distribute in groups examples of a miracle, parable, teaching, event from JC's life, and in groups ask the students to say what about it points to JC being the son of God. Give ten minutes, and then get them to feed back to the class.
Plenary: Either one thing they've learned about JC today that they didn't know, or do they think from the evidence that he was or wasn't the son of God.
There is a series of lessons on www.standards.dfes.gov.uk/schemes3 that deals with a generic religious figure, and is for Year 7, but is usable for year 8.
Hope that helps.