Some schools are able to boast extraordinary clusters of the great and good or the just plain famous. But is it something the schools do or just coincidence?
Go and look at your old school's Wikipedia page. Roughly three-quarters of the way down the page there is usually a section listing notable past pupils.
Some are household names - musicians and TV presenters. Others are unknown to most, but are still at the top of their field - captains of industry, research scientists and diplomats.
If you can't find that alumni section it may be because no-one from your school went on to become famous. It could be that your classroom wasn't in one of these "celebrity schools".
Major public schools like Eton are well-known for their track record of turning out famous alumni. David Cameron was the 19th British prime minister to attend the school near Windsor. But what about ordinary state schools? There are plenty with clusters of famous ex-pupils.
Just a few miles from Eton is Drayton Manor High School in London. Past pupils at the comprehensive include singer Jay Kay, the front man for Jamiroquai, England and Tottenham footballer Peter Crouch and rock star Rick Wakeman.
Over on the other side of the capital is St Bonaventure's Catholic Comprehensive School. Nicknamed St Bons, the east London boys' school produced England and Tottenham footballer Jermain Defoe, chart-topping rapper Tinchy Stryder, 2005 Apprentice winner Timothy Campbell and Conservative MP David Amess.
There are plenty of clusters outside London as well.
The Liverpool Institute, now closed, had Beatles George Harrison and Paul McCartney, along with their road manager Neil Aspinall, the newsreader Peter Sissons and theatre producer Bill Kenwright all at the school at the same time.
Belfast's St Malachy's College is the oldest Catholic grammar school in Northern Ireland. Many former students went on to positions of influence. But as well as the judges, politicians and bishops that attended the school, so did TV presenter Eamonn Holmes, actor Ciaran Hinds and football manager Martin O'Neill.
North London comprehensive Haverstock School also boasts a mixed set of famous students. The leader of the Labour Party, Ed Miliband, and his brother David went there. But so did all three members of the successful hip-hop group N-Dubz and former Labour MP Oona King. Footballers John Barnes and Joe Cole are also former students, as is actor Steve McFadden who plays Phil Mitchell in Eastenders.
Lesser known independent schools
- South Hampstead High School: Author Fay Weldon, model Daisy Lowe, actresses Helena Bonham Carter and Olivia Williams
- North London Collegiate: Actress Rachel Weisz, Vogue editor Anna Wintour, TV presenter Esther Rantzen
- Latymer Upper School: Actor Hugh Grant, chef Heston Blumenthal, model Lily Cole
Head teacher John Dowd says the school has a diverse set of students. Half its pupils are entitled to free school meals, more than half are bilingual and 23% are refugees. He believes N-Dubz's feats demonstrate that success can also come for students who aren't just academic.
"We try to generate a culture of high aspiration and success in any field is something to be lauded, whether that's in sport or politics or on television."
Some successful former students also come back to help the current pupils. David Milband comes into the school on Tuesdays to teach politics and mentor pupils.
That belief in students is something Michael Portillo thinks is important in a school - but is lacking in many. He went to Harrow High School - not to be confused with the famous fee-paying Harrow School. He graduated the year before his school moved from grammar to comprehensive status - going on to become a government minister and later a TV personality - along with a cloud of famous alumni.
In an old school photo he is standing next to the former barrister and TV presenter, Clive Anderson. Their classmate was Sir Nigel Sheinwald, the current British ambassador to the US. In the same year over at the girls' school was Diane Abbott, who went on to become the first black woman to be elected to the House of Commons and is Portillo's partner in punditry on the weekly politics programme This Week.
Portillo attributes his success to "warm", educated, intelligent and dedicated teachers. He also adds that he and his classmates had ambitious parents who had "lots of books in their houses".
But for him the main reason the school was successful was the competitive environment.
"Twice a year we got our exam results and everyone would know each other's results," he says. "In my class there were three of us who competed for the top spot."
Paul Nurse was two years above Portillo. He went on to become Sir Paul, the Nobel prize-winning president of the Royal Society.Location, location, location
House music DJ Judge Jules says it wasn't what was taught in the classroom that made many pupils in his former school successful; it was down to its location in a middle-class area. He says it meant there were a high proportion of "pushy parents".
He went to Highgate Wood comprehensive in north London, as did the BBC's business editor Robert Peston, DJ and singer Sonique, former England footballer Laurie Cunningham and fashion designer Ozwald Boateng.
Jules says his parents expected a lot from him academically, which was typical for his "suburban" area. He got into DJing while he was studying law at university.
But for the former chief inspector of schools, Chris Woodhead, the main determinant of a successful school with a healthy output of golden alumni is the head teacher.
He picks out Elizabeth Sidwell. Currently England's schools commissioner, Dr Sidwell was the headteacher at Haberdashers' Aske's Hatcham College in New Cross, south-east London. The alumni of this school include newsreader Fiona Bruce, footballer Shaun Wright-Phillips and singer-songwriter Katy B.
It would seem, anecdotally at least, that many of these "celebrity schools" are in London. That might be down to anything from the economic dominance of the capital to the fact that many of the great and good gravitate there and so school their children there.
What is clear is that there are plenty of diverse opinions on why schools might produce famous alumni, often from the alumni themselves, but nobody can really establish a formula for a good school.
In the end, it might all be coincidence.