As the government threatens to force another 400 failing primary schools into academy status, the number below the floor standard in Norfolk looks to have halved – without the need for a sponsor.

Teaching unions have questioned whether the plans, announced by David Cameron earlier this week, are the best way to encourage improvement, insisting there was no proof that academy status automatically led to higher attainment.

It comes as Norfolk County Council said it expected this year's Key Stage 2 league tables, which will be published by the Department for Education next month, to show far fewer of the county's schools missing ministers' minimum standard.

Alison Thomas, cabinet member for children's services, said: 'The number of schools below the floor standard has almost halved compared to last year, which is positive news.

'This has been due to the incredibly hard work of the schools involved and confirms that our intervention to ensure the schools have the right approaches to teaching, learning and governance is appropriate and working.'

Last December, there were 43 Norfolk schools below the floor standard for KS2 – meaning they had fewer than 60pc of children achieving at least a level four in English and maths, and progress levels in both subjects were also below the national average.

The DfE said it would base its selection of the bottom 400 primary schools on those who were consistently below the floor target.

Just three Norfolk primary schools have chosen to convert to academies since 2010, with a further three becoming sponsored academies.

Among the schools to pull themselves above the floor standard since last year is George White Junior School in Norwich, which has 'no firm plans' to become an academy.

Headteacher June Sewell said she believed academy status was right for some schools but it had to be done as a partnership rather than something imposed on them.

She added: 'This school has improved hugely, but we haven't done that by ourselves. We've done that with the support of the local authority, and with the support of the schools in our cluster.

'The government talks a lot about headteachers and schools taking ownership – that's what we've done.'

Both the Norfolk branch secretary of the ATL teaching union and the regional officer of the NUT said they were against the government's academies policy and any decision to force schools to change their status.

Andrew McCandlish, of the ATL, said: 'There's no real evidence that they actually do any better than maintained schools. Really, it's a question of pursuing the policy irrespective of proven outcomes.'

County councillor Mrs Thomas said the authority was constantly talking to schools about how they could improve and discuss a number of options including partnerships with other schools, federations and becoming academies. 'Whichever solution works best for them,' she said.