I’m off to the Houses of Parliament with Year 6. I have been a Londoner all my life but never done the tour, so it’s an ideal opportunity.

The children get into pairs and we file to the bus stop. It’s a squeeze but we’re all able to get on the same bus, spreading along its length. Almost immediately, Sadie feels sick and I watch a couple of passengers shift cautiously. Fortunately she’s not in my bit of the bus and one of the teachers has plastic bags.

She tells Sadie to breathe deeply and look straight ahead. The bus trip is short, Sadie’s fine and soon we’re walking along Horse Guards Parade and into St James’s Park. It’s a glorious Autumn morning and I think how lucky the ducks are. A beautiful park, a rippling pond to swim on and passers-by with lots of bread.

Although it’s relatively early, the teachers decide we should have lunch now rather than carry bags around the Palace of Westminster. The children sit on the grass and unpack their lunches. Michael doesn’t have one because his mother couldn’t be bothered. I had anticipated this and before coming out I had nipped into the kitchen and asked our cook if she would prepare salad rolls. one for me and one for Michael.

She has included yoghurts and bananas, so Michael is well fed. He likes the yoghurt but rejects the banana, offering it to an inquisitive squirrel instead.

Olamide has cake in his packed lunch. Not a slice, mind: an entire cake. Similarly, Yassim has a large packet of custard creams. I wonder what their mothers were thinking and then realise they probably gave their offspring money to buy their own packed lunch. Neither parent seems to be enthusiastically supporting our anti-obesity drive.

It is time to move on and we arrive at the Houses of Parliament security. The children are intrigued to find that their photos need to be taken and our belongings passed through scanners. My tray sets off the buzzer and I realise there is a metal spoon in my bag. The cook had slipped it in so that I could eat my yoghurt.

We enter the palace and the classes separate off with the guides. Our guide is terrific and gives the impression we’re the first party he has ever shown around, answering the children’s questions at just the right level. He throws in fascinating titbits, pointing out the wall concealing the royal toilet in the Queen’s Robing Room, plumbed in Queen Victoria’s time while the sewers were being built. “Before that,” he says, “waste would go into the Thames and smell pretty grim in the hot summer days. That’s why MPs needed long holidays.” “Well, it don’t smell now,” William says. “But they still have long holidays.”

Our guide falters only once. We sit on benches opposite shelves of large red tomes and he fetches one down, explaining that this is Hansard, and everything said in Parliament is recorded in these big red books. He asks for questions and Lyndon raises his hand. “What are those big red books?” he asks. For a moment our guide thinks Lyndon is being cheeky, but then he’s not familiar with Lyndon’s attention span.

We pass through the debating chamber and Amid shows concern at the damage that Black Rod is doing by hammering on the door. At the end of the tour we reach the book stall and Sarah discovers the free brochures and booklets. Word spreads and soon every child has an armful. I think of the burden on our taxes.

But as we board the bus for school I realise how much I have enjoyed the morning. I must get out more. And there’s a bonus: I’ve missed Braidon’s mum, who was up complaining yet again.

• Mike Kent is headteacher at Comber Grove Primary in Camberwell, south London. Email: mikejkent@aol.com.