The head of education in Suffolk last night pledged to overhaul standards in the classroom after the latest primary school results confirmed the county is still one of the worst-performing authorities in England for attainment levels among 11-year-olds.

Some 73% of 11-year-olds in Suffolk attained at least a Level 4 grade – the standard expected of the age group – in reading, writing and mathematics in the national curriculum tests, known as SATs, this year.

It is a rise from 70% last year, meaning more children in Suffolk are reaching the standards expected of them in the three Rs by the time they leave primary school.

However, the average for all schools in England increased by a slightly higher amount, from 75% to 79%.

It means whereas Suffolk was only 5% behind the national average last year, it is now 6% adrift.

Last night, Lisa Chambers, the cabinet member for education and skills at Suffolk County Council, issued a staunch defence of the authority’s flagship reforms, dubbed Raising the Bar.

She revealed the authority has set a target of exceeding the national average by 2017 and insisted a plan agreed with headteachers will achieve this.

This year’s score of 73% in the SATs exams means Suffolk is now ranked as the joint seventh-worst local authority for attainment at Key Stage Two in England. Suffolk was ranked the joint fifth-worst last year. Suffolk is below every London borough. The Government data is provisional, meaning positions could change.

Ipswich MP Ben Gummer said the results are an “embarrassing indictment” of education in Suffolk, but stressed the county council is showing a greater urgency to boost results. Mrs Chambers said: “It is very encouraging to see that more of Suffolk’s 11-year-olds are achieving the levels expected of them in reading, writing and maths. I would like to congratulate the teachers, heads, governors, parents – and of course the children – for their hard work and dedication.

“We knew Suffolk would not reach the national average this year. I don’t think anyone expected that to happen so quickly. But we do have a detailed plan, developed and agreed with Suffolk schools, to accelerate progress and get the county above the national average in the next three years. We will continue to work with, and challenge, schools to drive up educational attainment. That is the direction we set with our Raising the Bar programme and is now what education professionals across the county are united around.”

Her remarks come after a damning Ofsted report last December found 33% of children in Suffolk do not attend a primary school rated “good” or “outstanding” – affecting 30,000 pupils.

Broken down, the SATs results found girls adhered to tradition by outperforming boys. Some 77% of girls attained the three Rs, compared to 69% of boys – and 36% of boys failed the standard grammar, punctuation and spelling test.

Mr Gummer said: “This is an embarrassing indictment of what is going wrong with education in Suffolk. We are making progress but it is still slower than the rest of the country.

“The gap between Suffolk and the rest of England is not closing, which is what we need to see. (But) there have been some fantastic results from some schools in my constituency that until recently had been written off (and) my most recent meetings with the county council have shown a urgency that was not there before.

“They are prepared to be tough to force change. We are improving but we are still bottom of the class. The really hard work is ahead of us.”