I should have anticipated the questions. They're always the same. You spend 10 minutes banging on about how interesting the latest class trip is going to be, how lucky we are to get out and see things, how - dare I say - educational it will be. But all the time you're waving down a sea of hands which are just waiting to ask the inevitable. Finally, you must succumb.
"Will there be a shop?"
Whether it be a trip to Hampton Court, the greatest Hindu temple outside of Asia, or an outing to the local nature reserve, it's obvious what will be the highlight. I can only imagine that had Christopher Columbus crewed his ships with primary school children, he'd have faced a similar interrogation.
"Can we bring spending money?" "Are we allowed Pokemon cards?"
This time round we're visiting a water treatment works as part of our geography unit. Not the most riveting of destinations.
The children are further disappointed to learn that my promises of lots of poo and general smelliness have come to nought as it's actually a place that filters water from reservoirs, rather than an actual sewage treatment facility. Still, I think the mums are relieved.
Thames Water is so concerned that an unruly bunch of 10-year-olds will be drowning themselves in the filter beds that they've insisted on a ratio of one adult to every four children.
In theory this relieves some of the supervisory load from me. In practice, it means I've got half a dozen bigger kids to look after. And I can't even shout at these ones.
With the absence of poo, the kids find it hard to maintain their interest for the full hour of the trip, though Mohamed plays a blinder by distracting our guide from the general level of apathy by bombarding him with questions. I've never seen him so engaged. Maybe this is a general breakthrough in speaking and listening. Or maybe he'll grow up to have an abiding interest in the water cycle.
Lunch is at a nearby nature reserve. It's getting chilly now and Christopher has managed to forget both his packed lunch and his coat. Quite a feat given that they all had to display both as they lined up to leave the classroom. Luckily he remembered his head.
After a lunchtime game of football (another highlight) and the nature reserve shop (mayhem!) we decamp to an enormous bird hide. One of the boys is whistling.
"Mr Ogle, Mr Ogle. Trae says he can talk to the birds!"
"I can talk to birds," I assert. "Hello darling, can I get you a drink?"
At least the mums laugh.