What is modelled writing?

The words in bold are the teacher's words and the words in italic are the words written on the board:

Today we're going to write a description of the fight between Theseus and the Minotaur. This is our success criteria:

Learning objective:  To write about Theseus' journey into the maze
Success criteria:  Describe characters using adjectives and powerful verbs. Use capitals and full stops in the right places

I'm going to start with a description of Theseus' first impression of the Minotaur:

The Minotaur was an enormous beast.

I want to describe how terrifying he was, so I'm going to mention his claws and teeth:

The Minotaur was an enormous beast, with horribly sharp claws and teeth like razors.

It could be a good idea to include the sound and smell of the Minotaur to give the reader a really good impression of him:

He was wheezing and grunting and his breath was foul from the stench of the humans he had eaten for breakfast.

Now I think Theseus would want to quickly attack the Minotaur, so I'm going to go straight into the action:

Theseus did not waste a minute: he plunged his sword straight into the Minotaur's neck.

Now I need to think about the Minotaur's reaction:

The Minotaur screamed a terrible scream, louder than a hundred men. Blood gushed from his neck in a bright, red arc.

Let's read over what I've written so far:
  
The Minotaur was an enormous beast, with horribly sharp claws and teeth like razors. He was wheezing and grunting and his breath was foul from the stench of the humans he had eaten for breakfast. Theseus did not waste a minute: he plunged his sword straight into the Minotaur's neck. The Minotaur screamed a terrible scream, louder than a hundred men. Blood gushed from his neck in a bright, red arc.

At this point, the teacher might ask the children to look back at the success criteria to check that it had been adhered to. Children might be asked to look for adjectives and powerful verbs to check that they are there. 

They may be asked to look at the punctuation and check it is correct.

The children may then be asked if they could improve this writing in any way. The teacher may underline a sentence and then ask the children to discuss how they could improve this with a partner and then re-write it on their whiteboards.