"But Mummy Lets Me!" Why Children Test the Rules With Every Adult (and What Stops It)

"But Mummy lets me!" If you have a nanny, a babysitter or helpful grandparents, you've almost certainly heard it. Here's why children test the rules with every adult, and the simple thing that stopped it in our house.

Why written house rules changed everything for us

When we first had a nanny, I assumed she would simply pick up how we did things. But so much of family life runs on unwritten rules: who sits where, what happens if you get down from the table, how much screen time is allowed, what the bedtime routine looks like. What was obvious to me wasn't obvious to anyone else.

None of this was her fault. She was doing her best with the information she had, and my children, being children, were very quick to spot an opportunity. "Mummy always lets us" is a phrase every nanny has heard, and it is rarely true!

So one evening I sat down and wrote it all out: our rules for the house. Mornings, mealtimes, screens, bathtime, bedtime, treats and safety. It fitted on a single page, and it made a bigger difference than anything else we did. Everyone knew what was expected, the children knew we were all on the same page, and the testing calmed down remarkably quickly. The same approach works for anyone looking after your children, from grandparents to babysitters.

"The conversations that happen before a nanny's first day shape everything that follows. When families and nannies have both worked through their expectations in advance, the settling-in period is smoother, the children adjust faster, and the relationship starts from a place of clarity rather than guesswork."

Fanny Di Domenicantonio, founder and director of Fox & Cubs

Why children test boundaries with different adults

Whenever a different adult is in charge, whether it's a new nanny, a long-standing one, a grandparent or a babysitter, children naturally want to find out where the edges are. It isn't naughtiness. It's how they make sense of the world and feel safe in it. They are asking, "Are the rules the same with you? What happens if I push?"

If the answer changes depending on who is in charge, children learn that rules are negotiable. That's when the battles start: the extra five minutes of screen time, the "just one more story", the meltdown when the nanny says no to something Mum said yes to last week.

Consistency is what makes children feel secure. When everyone responds the same way, children stop testing quite so hard, because there is nothing to gain. And when the rules are written down, they don't depend on anyone's memory, mood or energy levels at the end of a long day.

How to create house rules that everyone sticks to

1. Agree them as parents first. If you and your partner aren't aligned, your nanny will be caught in the middle. Sit down together and decide what really matters to you.
2. Organise them around the day. Mornings, mealtimes, screens, bathtime and bedtime, treats, and safety. This makes the rules easy to follow in the moment, rather than a list nobody remembers.
3. Be specific. "Be good at the table" means something different to everyone. "Sit at the table to eat, and ask before getting down" is clear to a child and to an adult.
4. Say what happens next. A boundary only works if everyone follows through in the same way. Write down the calm, simple consequence, such as "if they get down from the table during a meal, the meal is over", so your nanny doesn't have to invent one on the spot.
5. Include the positives. Rules aren't just about what children can't do. Write in the moments to notice and praise, like praising them as soon as they sit down at the table. Children repeat what gets attention.
6. Share them in advance. If your nanny is new, give her the written rules before her first day, not on the morning itself. The first day is overwhelming enough already. If she's been with you a while, sit down together and go through them over a cup of tea.
7. Share them with your children too. Tell them, "These are our family rules, and they're the same whoever is looking after you." This takes away the "but Mummy lets us" argument before it starts.
8. Review them regularly. Children grow and routines change, and even with a nanny who has been with you for years, small exceptions can quietly become the norm. Look at the rules together every few months and update them.

A peek at our own family rules

Here are some of the rules from the page I wrote for our nanny all those years ago. You'll see they aren't complicated. They are just clear.

Mornings

• Bedroom jobs are done before breakfast: pyjamas folded, duvet straight, curtains open and fully dressed.
• Getting out of the house always takes longer than expected, so allow extra time!
• Make sure coats, school bags and shoes are all ready.

Screens

• Ask before going on the computer, with a timer set for 20 to 30 minutes.
• No TV on weekdays. It's a weekend treat.

Mealtimes

• Everyone sits at the table to eat. Praise them as soon as they sit down, so they want to stay there.
• They need to ask to get down from the table, and take their plate to the dishwasher.
• Stick with the meal you've served. Don't offer alternatives, but they don't have to eat everything.
• Keep the atmosphere positive and chat about their day.

Encouraging good manners

• If something is asked for rudely, or a please or thank you is forgotten, do an "action replay" and try again.
• When they ask politely, notice it and say so: "You asked so nicely, thank you!"

Bathtime and bedtime

• Clothes in the laundry basket, wee, then bath.
• Splashing water over the side means bath time is over.
• Teeth, pyjamas, then stories and the saying goodnight routine.
• Pop back in after a few minutes to praise them for staying in bed.

Treats

• Unless we've agreed it beforehand,  don't buy them sweets or ice creams bought when out.
• You can take along a small treat and give it to them once you've arrived somewhere successfully - it helps to motivate them along the way!

Safety

• Hold hands when crossing the road, and have them wait at the kerb and tell you if they think it's safe to cross (it helps them understand road safety).
• On bikes, have the kids wait to be told when to cross.

The detail is what made it work. Our nanny never had to guess, and the children quickly learned there was no point trying a different answer with a different adult.

Getting your child to listen to everyone

Written rules give everyone the same script. But children listen to the adult, not the piece of paper. A few things help your child listen to you and your nanny alike:

• Connect before you direct. Get down to their level, engage in what' they're doing and make eye contact before asking them to do something.
• Say it once, calmly, and follow through. Repeating yourself teaches children they don't need to listen the first time.
• Notice the good stuff. Specific praise ("You came straight to the table when I asked, thank you") works far better than nagging.
• Keep handovers predictable. A simple handover routine, with the same words in the same order each morning, helps your child know what to expect and settle quickly with the adult who's staying.
• Back each other up. If your child says "but Mum lets me", a calm "Our family rules are the same whoever is here" is all that's needed.
• Responding to rudeness towards the nanny, grandparent or babysitter. Catch it quickly, don't use shame but say something like "That doesn't sound like how you normally ask for something Henry, you just need to try that again and ask [name] in a polite voice". 
• Listen to your nanny. Ask her what she's noticing. She'll often spot things about your child's behaviour or routine that are hard to see when you're living it every day.

When parents and nannies work as a team, children feel secure, and family life becomes calmer for everyone.

Want more practical tools?

Download my free guide, How to Get Your Kids to Listen Without Nagging or Threatening. It's packed with simple strategies you can use straight away, and share with your nanny too.

If boundaries feel like a constant battle in your home, I'd love to help. Book a free discovery call and we can talk about what's going on and how to make things easier.

This post was written in partnership with Fox & Cubs, an award-winning nanny and private staff agency helping families find the right childcare.