Axing school league tables in Wales has not had a positive impact, according to new research.
A study carried out by academics at Bristol University concluded that schools have performed worse since tables were abolished in 2001.
Researchers compared schools in England and Wales before and after they were axed in Wales. League tables are still used in England.
"We find systematic, significant and robust evidence that abolishing school league tables markedly reduced school effectiveness in Wales," the research document stated.
"The impact is sizeable: a fall of 1.92 GCSE grades per student per year."
Researchers concluded that the abolition of league tables has had the biggest impact on the worst-performing schools.
Speaking earlier this year, Nick Seaton, chairman of the Campaign for Real Education, suggested that some schools encourage pupils to take easier subjects in order to boost league table rankings.
He said the organisation regularly receives complaints from parents whose children are unable to study the subjects they wish.