I suffered a sense of humour failure at 3.15am on day four of our recent residential trip. I expect to be up at all hours when taking 60 primary school children on a week-long outing – especially when many of them haven’t left home before. I expect to be sleep-deprived, in loco-parentis 24/7, dealing with everything from homesickness and travel sickness to shampoo leaks and lost underwear.

In fact, some of my fondest teacher memories come from residential-trip disasters. Like when Daniel mistook his shower gel for suncream and lathered up on the beach, when Ava brought five outfits for the disco but none for rock-climbing and had to do every activity in a glittery dress, or when we discovered Jess was a terrible sleepwalker. It’s all part of the adventure.

This time, however, after less than four hours’ sleep in three days, it wasn’t fun. It had become a battle – and one we were losing. Part of the reason we take children away for a week is to develop independence, and we carefully design the week to do just that. We ask that pupils don’t bring mobile phones or laptops, electronic games or items of value that could get lost or broken, and that they don’t fill their bags with tonnes of sweets and snacks. We make some some allowances in this respect by asking them to bring treats to share with the group, which we dole out at appropriate times, such as around the campfire or on a hike. We also ask them to bring no more than £5 spending money, which is plenty for a gift shop full of key rings and snow globes.

I think the rules are really quite reasonable; I can’t imagine that many parents at home would load up their 10-year-old with electronic gadgets and Haribo to take to bed, or send them to the local corner shop with a blank cheque to blow on cheap plastic. Of course, there are always a few who push the boundaries, but mostly it’s easily managed.

Not this time. On the first night, two children were sick and we confiscated more than two kilos of sweets and biscuits from just one bedroom. By the second night, an entire friendship group had fallen out through instant messaging on their phones and DS consoles which went on into the early hours. On day three, several children wouldn’t eat breakfast because they’d gorged themselves in their rooms so much. As a result, one was sick on the paddle boats.

We conducted a quick room search and removed much of the contraband, including a full sports bag of snacks from one child, but inevitably much was hidden and we hadn’t packed sniffer dogs. By the third night when my sense of humour finally failed in its entirety, there was a full-blown criminal investigation underway – including phone calls home – to establish what had happened to the £50 cash a child had been given which had disappeared from the “secret” pocket in her bag.

You might wonder why controls weren’t tighter and why the children were allowed these items in the first place. The short answer is: they weren’t. These are primary-aged children, not hardened criminals. It had been made very clear what they should and shouldn’t bring, but their parents had taken the conscious decision to flout those rules and provide their children with the very “treats” that ruined the trip. In fact, one parent shouted at me saying I didn’t have the right to cut off her communication with her daughter by taking away her mobile phone, despite the fact all parents had been given two phone numbers to call if they needed to get hold of their children at any time and had signed a form agreeing to the rules we put in place.

I should briefly put my complaints in context: at least half of the children were an absolute delight to take away and had done everything we asked of them. They had a lovely time. But I was left feeling angry and undermined by parents who expected the staff to give up their week of sleep and sanity, working round the clock, to deal with the nightmare they had willingly created. Some even giggled as I handed back the items we’d confiscated, one commenting: “D’oh! You were caught then!” before opening the returned sweets to feed her child in front of me.

Not only was the immediate situation a problem, but the attitude of not having to do what the teachers say, which was promoted by some parents, seriously damaged the authority we needed to manage the trip successfully. Bearing in mind we spent a week responsible for their children’s care and safety, I’d have thought parents would want to work with us, not against us.

As for the £50, it turned up. It was in the child’s coat pocket, which she’d left in the food hall. We allowed her to spend £5 of it, which I thought was a reasonable compromise, and locked the rest away until we got back to school. She sulked for the whole week and still hasn’t forgiven me. Her father’s reaction? “It is supposed to be a treat for the children. Aren’t they allowed to have their fun?” Yes, it’s a treat, but also also a carefully planned learning experience. And you ruined both.

Follow us on Twitter via @GuardianTeach. Join the Guardian Teacher Network for lesson resources, comment and job opportunities, direct to your inbox.