The two men in their 20s start rearranging the classroom. Tables are stacked up. Chairs moved into a square.
"It is important to set up the room," says Darren Laville, schools training co-ordinator with Birmingham's homeless charity St Basils.
"It makes them realise they are stepping into our zone."
Shortly after, the class of about 25 Year ten pupils start filing in after spending a gloriously sunny lunchtime out-side in the extensive playing fields of Solihull's Langley School.
They shuffle uneasily into their seats. In the corner sits a slim young man wearing jeans, T-shirt and a blue cap.
The session starts with Darren asking if the 15 and 16-year-olds have heard of St Basils. Only two pupils have.
Darren then introduces the class to a stick character drawn on a whiteboard. He tells the pupils the person's age - 16 - address and main relationships: mother, youth worker and boyfriend.
From there on the class is asked to build up the imaginary teenager's profile.
"Is Jay a he or a she?" asks Darren.
"Where does she live? What kind of music does she listen to? What does she wear?"
As the pupils answer, Darren scribbles down the information on the board.
"Where does she spend her time?" he says.
"With her boyfriend," responds a pupil.
"Does she like school?" "No. She would rather be with her boyfriend."
"What about her friends?" "She doesn't like her friends anymore, she only likes her boyfriend."
Up to now Jay could be any typical teenager. But then things turn a bit darker. The pupils decide Jay's boyfriend is a bad influence on her.
"Why?" asks Darren. "He gets her into bad things. He has a reputation for doing drugs."
As the youngsters develop the profile, it turns out that Jay's mother also smokes and drinks - a habit she gained from Jay's father who has now left.
Jay has not got any hobbies - the family is too poor to fund them and she is becoming reliant on drugs.
A picture of a troubled teenager is fixing into their heads.
"Every human being has three basic needs," says Darren.
"Physical, emotional and social. We are going to look at how we get these needs met in our home."
He gets the pupils to consider how they relax in their homes, focusing on the lounge, bedroom and bathroom.
The teenagers paint a picture of normal domestic life - lying on a sofa in front of the television, socialising with friends in their bedroom, eating dinner with their family.
Darren then gets the youngsters to imagine how they would feel deprived of these things in each room.
Words like "restless", "frus-trated", "tense", "moody", "embarrassed", "paranoid" and "angry" fly out of their mouths.
"Would you agree with me that someone sleeping rough on the streets is not having their needs met?" asks Darren.
"Yes," reply the class. The youngsters then open a series of envelopes, charting Jay's bleak progress down the ladder.
"Jay's situation has changed," reads a pupil.
"For two weeks she has been sleeping with friends on floors and sofas."
Another pupil opens the next letter.
"Jay has outstayed her welcome. For the last three nights she has slept on the streets."
The pupils discuss how she might now feel before Darren reads out the final note.
"Jay has begun to speak to other rough sleepers. She has met up with a guy who has been sleeping rough for a year."
He then highlights the venerability Jay now has of falling into crime, drugs and prostitution.
At this point, Anthony Richardson - the 25-year-old seated in the corner - stands up.
"When I was about 12 or 13, I lived with my parents," he says.
"There were rules and regulations and I didn't like them. My mum used to beat me. I wasn't happy so I ended up in a children's home."
Anthony goes on to explain about the deprivation he experienced living on the streets. He ends by warning homelessness is something that could happen to anyone.
The silence that followed spoke volumes about the impact of the session.
Afterwards, David Evans, head of pastoral care at Langley, summed it up well.
"All this stuff is in text books but there is nothing more effective than having these guys in front," he said.
"These kids come from good supportive homes, but home-lessness could happen to anybody. It really changes their stereotypes."