A website designed to present Ofsted reports and exams data in an accessible way for parents has come under fire from headteachers for providing "over-simplified" information.
Schooloscope describes itself as "an honest, independent, straightforward guide to how your local schools are getting on", which tries "to tease out something interesting from the dry tables of statistics".
But heads' union the NAHT said its school ratings are taken "out of context", and warned that the website's conclusions are "subjective".
Each school is illustrated by a cartoon building, with a smiley or sad face to show how "happy" its pupils are, and a green, amber or red roof depending on its exam results. It is also given a generic description, depending on how it has performed in Ofsted reports and exam grades.
Describing one struggling school, the website says: "The kids here are facing a few difficulties, and the school isn't showing many signs of improving. We feel concerned about the challenges facing this school." Each school is also ranked by exam results in relation to other schools in its local authority area.
The NAHT has warned that the site's use of "cut and paste" phrases fails to reflect the nuances of a full Ofsted report, and that the generalised statements "are not hugely informative and are, in essence, subjective statements".
NAHT general secretary Russell Hobby said: "I don't have a problem with the intent or sincerity behind the site, but the information is over-simplified and out of context.
"It uses raw data and attempts to convey phrases which are very carefully coded, so it doesn't necessarily say what they mean. I looked up my child's school and the data was from an Ofsted report five years ago - it's out-of-date."
Matt Webb, chief executive of design consultancy BERG which runs Schooloscope, said: "This summary is a simplification, yes. It's a simplification because the language of Ofsted reports and Department for Education performance tables can be daunting to many people.
"Schooloscope provides a friendly, human way in which to understand what these statistics mean.
"Once you have a handle on the stats, we provide links to the original report and performance tables so you can read it yourself and come to your own conclusions."
WEIGHTS AND MEASURES
In a league of its own?
- Pisa measures the success of schools in 70-plus economically advanced countries
- It has assessed international standards in reading, maths and science in 2000, 2003, 2006 and 2009
- The Government uses the UK's relative decline in Pisa over the past decade to support its argument for reform
- But this includes the 2000 results, which the OECD now says are statistically invalid
- Ministers have not highlighted Trends in International Mathematics and Science Study (TIMSS) in which England performs much better than in the Pisa rankings.