The results of the key stage two tests taken by pupils across the borough showed 72 per cent of pupils had passed maths and English at the benchmark level four.
But the figure means the borough remains adrift of the national average of 74 per cent - which also remained static - and has been overtaken by Barnsley as the best performing authority in South Yorkshire.
The statistics also show Doncaster has lost ground on its achievements of three years ago, when pupils’ performance matched the national average - then rated at 73 per cent.
Conservative councillor Jonathan Wood has now called for talks with education bosses at the borough to find out why the improvements appear to have lost momentum.
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Coun Wood, a former member of the council’s ruling cabinet, said: “Clearly it’s disappointing that we have not made the national average this year.
“I think at this point it might be sensible to ask a few questions of our education professionals to see if it’s a statistical anomaly or if there is something more fundamental.
“We have to recognise we are behind the national average and find out what the root cause is.”
Doncaster’s youngsters performed best in maths, with 80 per cent reaching the benchmark standard - the same as the rest of the country.
But they were less successful at English, where the figure was 78 per cent, compared to 81 per cent nationally.
Boys and girls in the borough performed at the same level in maths, but the boys lagged behind the girls in English - with 72 per cent of boys reaching level four compared to 85 per cent of the girls.
This years figure also saw Doncaster lose its status as the top performing authority in South Yorkshire, a position it had held since 2007.
Barnsley now tops the table, with 73 per cent of pupils there reaching the benchmark in maths and English.
But Doncaster remains clear of the other two South Yorkshire authorities, with Sheffield’s figure recorded as 70 per cent, and Rotherham rated at 68 per cent.
Meanwhile the National Association of Head Teachers highlighted the importance of recognising the hard of work of all Year Six pupils who took the tests this year.
A spokesman said: “We should remember that behind the tables and statistics are thousands of individual success stories which should not, and must not, be lost in the debate about ‘standards’ in our schools.”