The National Association of Head Teachers (NAHT) has argued the results are too "unpredictable", because there was "inadequate time" to implement the new curriculum.
The association urged the education minister to "consider some changes" after collating feedback from members.
"Unfortunately, significant mistakes have been made in the planning and implementation of tests this year, with a negative effect on children’s education," Russell Hobby, general secretary of school leaders’ union NAHT, told The Huffington Post UK.
"The tests are not seen as helping teachers to teach or providing reliable information to parents about the progress of their children.
"We want to find a clearer, simpler system that gives parents and schools the information they need to improve children’s learning."
The letter began: "The experience in a large majority of schools has not been a positive one.
"It is not just that the marks may be lower overall, which could be addressed, but that they will vary in unpredictable ways.
"We know of widely different approaches to writing assessment across the country, for example.
"And the content and sequencing of the reading test meant that lower attaining pupils had little opportunity to show their progress."
It concluded: "School-level scores should not be published externally.
"In our view a hold on external publication, until we can be sure what the data is telling us, would be a sensible step."
Another issue the NAHT wished to address with Morgan was a commitment to changing assessments of writing.
Currently, to be working at the expected standard in writing, children must meet all of the government’s 18 criteria, including spelling.
But headteachers are concerned this process labels some children as working "below" the expected standard because they miss out on one or two criteria.
The letter points out that the top grades at GCSE and A level don't always require 100%, but at the end of Year 2 and Year 6 children must get 100% to meet the expected standard of writing.
As a solution, the union asked Morgan to move from taking a "secure-fit" approach to judgements in the assessment of writing, to a "best-fit" approach which would account for children who are close to 100%.
"We believe that the suggestions we have outlined above would go some way towards settling growing disquiet about assessment and demonstrate a clear faith in the profession to deliver the government’s reforms," the letter ended.
In response to the letter, a Department for Education told The Huffington Post UK: "We have reformed the primary curriculum to help ensure all children leave primary school having mastered the basics, and the support and hard work of teachers is key to making this happen.
"We are determined to get this right and remain committed to working with teachers and headteachers as we continue with our primary assessment reform.
"We will respond to this letter in due course."
The full open letter can be read below.
Following SATs week, we have collected the feedback of members and urge you to consider some changes to the current and future arrangements for assessment. The experience in a large majority of schools has not been a positive one.
Teachers and headteachers all agree that a thorough review of assessment is necessary. We hope that you will commit to a fundamental review of assessment to avoid further problems next year.
In the meantime there are two pressing concerns and possible solutions:
- Hold off on publication of any 2016 test data
- A commitment to changing from ‘secure fit’ to ‘best fit’ judgements in the assessment of writing
Publication of Data
Given concerns about both the design and administration of the new assessments, the lack of preparation for schools, the inadequate time to implement the new curriculum for the current cohort, and the variations in approaches between schools resulting from delayed and obscure guidance, it is hard to have confidence in the data produced by this round of assessments.
It is not just that the marks may be lower overall, which could be addressed, but that they will vary in unpredictable ways. We know of widely different approaches to writing assessment across the country, for example. And the content and sequencing of the reading test meant that lower attaining pupils had little opportunity to show their progress. This may result in a skewed distribution of marks that simply setting a lower threshold may not solve. Comparisons between schools become very risky.
School level data should not be externally published under these circumstances. Assessment data should still be available on RAISE Online, which summarises a school’s performance at the end of each Key Stage, and could be shared with parents, but the aggregated school-level scores should not be published externally. We understand that Ofqual is already mandated to conduct a review of this year’s data. In our view a hold on external publication, until we can be sure what the data is telling us, would be a sensible step. In this interim year, we should be cautious about the data that’s been collected.
Problems have arisen with the new secure fit model; teachers need some sensible flexibility when assessing children’s writing and would be happier with a ‘best fit’ model. This would give a more accurate reflection of whether or not a child has grasped the overall skills of writing.
Children who are clearly excellent writers will be incorrectly labelled as working below the expected standard this year simply because teachers are not permitted to use their own judgement about their balance of abilities. We are particularly concerned about the impact on the thousands of dyslexic children in school.
There are few other tests or examinations at any other stage of education, where a student is judged by ‘secure fit’. The top grades at GCSE, A-Level and degree level are all attainable with a score below 100%, and yet only 100% will do if our six and ten year olds are to meet the required standard.
A move from ‘secure fit’ to ‘best fit’ would remove some problems. However, it is clear that the interim framework is not working and needs a sustainable long-term replacement.
Serious problems have emerged in the planning and implementation of tests this year, with a negative effect on schools. We believe that the suggestions we have outlined above would go some way towards settling growing disquiet about assessment and demonstrate a clear faith in the profession to deliver the government’s reforms.
Russell Hobby, general secretary, Kim Johnson, president, James Bowen, NAHT Edge director, Amanda Hulme, chair of NAHT’s assessment group.