"I've got just one question for you lot," he says, as heads turn expectantly. "Why do you call yourselves Gypsies?" The reply is immediate:
"Because we're proud of it.".
Mr Rees, 58, headteacher at Pembroke's Monkton Priory primary, is clearly no fan of political correctness. "To call these children travellers is to imply there is something wrong with the name Gypsy," he says, shaking his head. "These kids are not travellers, they are Gypsies."
Set within a sling-shot of spectacular Pembroke Castle, Monkton Priory boasts a new learning centre offering some of the UK's best facilities for Gypsy children.
Officially opened by education minister Jane Davidson earlier this month, the pound;750,000 building - funded by the Welsh Assembly, Pembrokeshire county council, the post-16 education funding agency Elwa, and the European Union - will also shortly offer a range of learning programmes for adults, including reading, computing and GCSE maths.
"This is the only Gypsy facility in the whole of Britain that has been inspected," says Mr Rees, who has taught at Monkton for 21 years. "The highest grade the inspector could give us was 'very good' - yet he actually referred to our centre as 'outstanding'. That was a very emotional moment for all of us."
Scenic the surrounding area may be, but Monkton has to cope with extreme poverty. Single-parent families are the norm and 20 per cent of the school's 244 pupils are Gypsies, most from the nearby Catshole Quarry encampment.
"Our early battle was for these children to access education up to the age of 11," recalls Mr Rees, "but if we were getting only two of them into the local comprehensive, then we were doing well."
Now around half the pupils reach secondary education, while some go on to college and one boy is studying civil engineering at university.
Bev Stephens, the teacher in charge of the centre, is now responsible for 210 pupils aged 11 to 16 from across the county, whose parents have no wish for them to experience secondary education. "A lot of these parents are very Victorian in their values. They are uncomfortable at the thought of their children receiving sex education at school or being exposed to drug culture."
Many Gypsy parents are unable to read or write, so the school will start its adult education courses shortly. "We want to equip people of all ages with skills for the job market," says Mr Rees. "Freedom is having a job and not being trapped in welfare."