Unless you’ve been living under a rock, you must have heard that Disney is releasing a new Mary Poppins movie. Just in time for the holiday season, Mary Poppins Returns continues the story of the nanny who is “practically perfect in every way.” She swoops into the home of the Banks family and sorts out not just the children but the parents as well.

It’s a wonderful story… but real-life nannies are very different.

I spend my life around nannies. I’m a stay-at-home mom in a neighborhood where the vast majority of mothers have paying jobs and employ a nanny to mind their kid during the day. At our local playground, it’s not uncommon for me to be the only mother sitting alongside eight to ten nannies.

But the more time I spend around nannies, the more I am convinced I would never hire one to look after my own children. There’s a great deal that could be said on this topic, but for now, I’ll list three of the biggest problems I’ve observed with nannies:

1. Nannies are Glorified Guard Dogs

A nanny’s primary concern is the physical safety of the child. I’ve witnessed this hundreds of times. The child’s development, their happiness, their socialization, etc., all come secondary to safety. Nannies worry that if the child gets hurt, they will be fired. I’m sure in many cases their employers assured them that accidents happen and it’s OK. But I don’t think the nannies believe it.

Some nannies take this to extremes. Recently, my two-year-old son and I waited in the lobby of my daughter’s dance school while she attended her ballet class. Another younger sibling was also waiting and she wanted to play with my son. However, any time she got near him her nanny told her to stop because it was “dangerous.” This lobby is basically a small room with a few sofas. What on earth did the nanny think could happen? In the end, she handed the girl a phone to get her to sit still.

I’m not reckless with my kids’ safety. But I also don’t deprive them of their childhood just to ensure they never get a single ouchie.

2. Nannies Resent Their Charges

Nannies earn less than their employer. That’s the only way for the arrangement to be financially viable.

But nannies are also human. Thus, it’s natural for them to be envious that the children they watch enjoy a more privileged lifestyle than they do.

I learned this the first time I ever interacted with a nanny. I was a college student, working a summer job in a neighborhood park in Virginia. I chatted quite a bit with the parks’ visitors, one of whom was a nanny who brought two young children almost every day. This woman told me in no uncertain terms how resentful she was that she had to leave her own daughter to go earn a living by watching these rich kids. At the time, I felt amazed the parents would leave their kids all day with a woman like that. As I got older, I realized how common such arrangements are.

Some of the nannies I meet seem genuinely fond of the kids they watch. But I’ve also witnessed plenty of instances of nannies being downright petty to their charges. They probably weren’t always motivated by resentfulness of the kids’ relative wealth, but I suspect that often they were.

3. Nanny-hiring Parents Don’t Know How to Look after Kids

When parents hire a full-time nanny, they are often left with no idea how to look after their child. When a parent spends 50 hours a week in an office setting – interacting only with adults, writing memos, going to meetings – it becomes very hard to switch gears and enter a child’s world.

I mentioned that I’m often the only mother at our local playground. That applies to weekdays. On weekends, it is usually parents, not nannies, who accompany the children. Would you believe I resolved a while ago to avoid the playground on weekends? When the parents are present, it becomes an angry, stressful place. I’ve witnessed too many nasty scenes of frustrated parents shouting at their kids.

A few weeks ago, a father verbally berated his son for an infraction that appeared to me to be nothing more than shyness. I realize I don’t have the full picture. Maybe there was more going on, but there was no justification for the way that father went off on him.

When the parents at the playground aren’t angry, they are often fussing over their child in bizarre, exaggerated ways. They constantly shove food at kids who aren’t hungry. They try to put sweaters on kids when it’s warm. These parents are clueless about the needs of their own flesh and blood. The nannies are better at looking after the kids for the simple reason that they spend far more time with them.

So go watch Mary Poppins Returns during your Christmas vacation if you feel like it. Enjoy! But please remember that it’s a movie and most real-life nannies are very different.