Image caption Pate's Grammar School in Cheltenham has been ranked the best in areas served by Trinity Mirror newspapers

Eight out of the 10 top-performing state schools in England and Wales are selective grammar schools, research by a newspaper group has found.

Trinity Mirror analysed 3,185 state-funded secondary schools in 15 areas for its Real School Guide.

About 5% of those analysed are grammar schools, which select pupils based on the 11-plus test.

The teachers union, the NUT, said selective schools were "socially divisive and antiquated".

Claire Miller, a data journalist for Trinity Mirror's regional team, said: "It's not too surprising.

"If you are selective you can select pupils who will do better, although a lot of these schools do also add value.

"Selective schools tend to have better attendance and more of their pupils stay in education after their GCSEs.

Top six Trinity Mirror schools 1 Pate's Grammar School, Cheltenham

2 Langley Grammar School, Langley

3 Queen Elizabeth's School, Barnet

4 Wallington County Grammar, Sutton

5 Nonsuch High For Girls, Cheam

6 Wilson's School, Wallington

"Of course, many will have their own sixth forms so it's easier for students to stay in an establishment with which they are familiar than start somewhere new."

Kevin Courtney, deputy general secretary of the NUT, said: "Children develop at different rates and at different times, which makes academic selection at 10 or 11 years old wrong.

"International evidence clearly demonstrates that if an education system is to be characterised by quality and equity, it is the comprehensive path that must be followed.

"Grammar schools have far fewer pupils with special educational needs or eligible for free school meals. They also have fewer pupils from ethnic groups."

What is a grammar school?

Image copyright Getty Images Image caption Trinity Mirror says grammar schools outperform comprehensives after analysing 3,185 schools

There are 164 grammar schools in England, educating 4% of the secondary school population.

Pupils are selected based on their results in the 11-plus test taken in the final year of primary school.

In 1998, the then-Labour government banned the creation of new grammar schools, although existing ones were allowed to continue.

David Cameron is also opposed to the creation of new grammar schools, preferring instead to allow groups to set up free schools.

Opponents of grammar schools say all children should be educated equally.

Supporters argue they give bright children from low-income families a better education on a par with private schools.

The Good Schools Guide says grammar schools can be found in 38 of England's 150 local education authority areas.

Trinity Mirror also found 88.3% of pupils stayed in education after completing their GCSEs with just 2.4% becoming NEETS (not in education, employment, or training).

The schools were judged on much more than just their GCSE results, said Ms Miller.

"There has been a tendency to focus on the number of A* to C GCSEs pupils get, but for many pupils that is not what's most important," she said.

"As a parent, you want to know a school is going to help your child reach their potential."

How have the rankings been worked out?

Image copyright BBC news grab

Data journalists from Trinity Mirror have analysed each school in 25 categories.

The number of A* to C graded GCSEs pupils gain is often used as a key indicator to a school's success.

But Ms Miller said other factors were important.

One important area of analysis is the value-added score, which is the amount a child improves across their time at the school.

Trinity Mirror has also looked at pupil-teacher ratios, attendance, truancy rates and what happened to students after their GCSEs: did they go on to further education, find employment or become a NEET?

This is the third year that Trinity Mirror has carried out the research, creating a page for each school on its various newspaper websites.

"It's the remit of local papers to inform and be helpful and give people information that's useful," Ms Miller said.

Trinity Mirror ranked Pate's Grammar School in Cheltenham as the top school in England and Wales, while three of the top 10 are in Sutton in Greater London.

Also in the top 10 are Altrincham Grammar School for Girls, Wolverhampton Girls' High School, Thomas Telford School in Telford and St Ursula's Convent School in Greenwich.

Click on the newspaper links below to see how your local school is ranked: