When the adverts for rather fabulous-looking private schools pop up in your Facebook Messenger app, you know it’s time to start thinking about choosing your child’s secondary school. 

Clearly, the algorithm thinks it knows what I am looking for in a school: ancient buildings, rolling hills and long-haired girls playing the violin.

But it has not yet picked up on my extensive use of a bank overdraft or the socialist DNA that excludes the private school option.

So a state school it shall be.

But where to start? In London, there seems to be an array of choice. Sometimes it feels as if there is a school bursting with children on every corner.

The first big challenge in our area is telling these schools apart. Ofsted has given most of them the suitably vague designation of “good”, which provides some welcome reassurance.

But my question to follow that, which the inspectors rarely manage to answer, is: “How good?” Their repetitive and bland terminology sends this mum into a daze.

Choosing a school ‘is like getting stuck in fog’

I turn to the school websites for help. They are, of course, all very professional affairs, everyone is smiling and the music department’s kettle drums look terrific.

But perhaps it is time to pierce beyond the gloss and plunge into the data.

Our nearest school proudly displays its “Progress 8 Score” of 0.11. Google tells me this is just above the national average of -0.03.

Well, if there was ever an underwhelming piece of information for a parent to see, it is this. The Attainment 8 score is not that much more enlightening.

As an education journalist, I’m well aware of the mind-boggling rationale behind these scores, which attempt to make schools focus on excellence across the board.

But they are rather useless for parents, who just want to know if it’s possible for their child to come out with a good clutch of GCSEs.

Likewise, the faintly snobbish EBacc measure that school websites display.

The uninitiated parent would have no idea if it is important, what it entails or whether they should worry about it. I’m glad Google is here to explain this half-baked, elitist and arbitrary concept.

So maybe the raw exam results themselves could help me to judge the schools?

I can just about get to grips with the concept of “percentage of pupils achieving five good GCSEs, including English and maths”.

And I am delighted to discover that Lily scooped ABD89877 in her exams this year and will be going on to sixth-form college.

But I asked for data, Michael Gove, not a car number plate. The new grading system should be comprehensible enough in a couple of years’ time when it covers all subjects, but for now, it’s another drain on everyone’s depleted mental energy.

Confused and exhausted, I ditch my data mining and decide to take a more human approach.

The open day dates are scribbled in my diary, and I write down questions for the staff: what is being done about pollution from the main road?

Do students get a chance to work on open-ended projects?

How does the school protect children from the pressure to achieve good exam results? Is there, on the off chance, any opportunity to have fun?

And if I do meet the head, what sort of a handshake am I looking for? A gentle squeeze or a knuckle-crushing alpha-clamp?

I also try to pick up clues from the pictures of headteachers on their websites. Does a head in a power stance, with his hands in his pockets, generally do a good job? And what about the resolutely formal head who does not give his first name on the staff list?

Some are entirely absent from their publicity materials. Are they selflessly letting staff and students take the glory or simply too scared to appear in public?

Amid all of this, choosing a school for your child does start to feel like a walk across the moors on a foggy day, trying to guess where the mental health quicksand and the bullying mantraps lie.

But perhaps I am worrying about nothing, and all this fretting is a waste of time. Once you rule out selective or private schooling, the distance you live from school is still a big decider when places are allocated.

Perhaps I chose my son’s school 12 years ago when I moved into our street.

Irena Barker is a writer and mother of three children