A teaching union leader has condemned advice from inspectors on how schools can achieve outstanding Ofsted verdicts as "game playing".
A study by not-for-profit company CfBT, which supplies the watchdog with inspectors, recommends schools aiming to receive Ofsted's top rating should try to "climb inside the inspector's skin".
It suggests schools adopt a pre-inspection process akin to exam preparation - studying previous reports and ensuring that all staff understand the watchdog's language.
However, Association of Teachers and Lecturers general secretary Mary Bousted said: "You can understand why schools take part in these game-playing activities.
"But the question that has to be asked is, does an outstanding verdict from Ofsted equate to an excellent school and better education for pupils? Quite often it doesn't."
CfBT is one of three bodies providing the privately contracted inspectors who lead more than three-quarters of Ofsted inspections.
Its researchers looked at eight secondaries that had made the leap from good to outstanding and found their heads "placed great store by how well they managed to create in schools 'a sense of urgency at the right time'".
They said the leaders had asked all staff to read inspection reports on schools already judged outstanding and held training sessions to ensure they "gained a strong grasp" of the difference between good and outstanding judgments.
"The schools placed great emphasis on the importance of everyone in the school knowing and understanding the language of the Ofsted framework," the CfBT report said.
Ofsted's top rating has become even more important for schools since ministers said all outstanding schools will be excused from further routine Ofsted inspections and given automatic approval to convert into academies.
But Dr Bousted said some schools would find it hard to achieve an outstanding judgment whatever they did because of their intakes.
Ofsted's inspection framework means schools with "low" raw exam results, regardless of pupils' background, are unable to achieve good or outstanding verdicts - except in "the most exceptional circumstances".
The CfBT report's authors, who include two former HMIs, also argue that a key factor in achieving outstanding is "going beyond tight quality controls" and becoming more self-confident and self-critical.
"You have to tighten up to be good. You loosen to become outstanding," one head told them.
Inspirational leadership, high expectations of pupils, a personalised curriculum and excellent teaching were also identified as factors leading to success in the report, titled To the Next Level: good schools becoming outstanding.
It said outstanding schools set challenging targets, tracked pupil progress, were "highly inclusive" and built good links with parents and local communities.
CfBT education director Tony McAleavy said: "The Ofsted framework can act as a catalyst for a useful professional discussion about the characteristics of excellence. It is a sign of a healthy inspection system that it can prompt school-level discussion of this nature and assist good schools to get even better."
An Ofsted spokesman said: "Teaching unions are absolutely right when they say schools should concentrate first and foremost on educating children.
"It makes sense for schools to learn from others' best practice and we would encourage schools to draw on notable case studies."
SIX OF THE BEST
CfBT says schools that go from good to outstanding have:
Inspirational leadership and high expectations of pupils
Research how Ofsted reached outstanding judgments and understand the watchdog's language
Set challenging targets and track pupil progress
Heads who create "a sense of urgency at the right time"
A personalised curriculum and excellent teaching
Are "highly inclusive" and build good links with parents and communities.