Some disaffected secondary pupils performed worse than their primary counterparts in trials of a new form of testing that could replace Sats, it was revealed this week.
In a writing test set at the same national curriculum level for children of all ages, younger children often outperformed older pupils.
The underperformance of key stage 3 children may help to explain the "unusual" results of trials of new tests that children can take whenever their teacher believes they are ready. Ministers delayed the release of results from the first set of tests in December to the 411 schools that took them until this month, after being surprised by the results.
Under the single-level test trial, any 7- to 14-year-old can be put in for an assessment at level 3 to 8. The new tests, if judged successful, could replace Sats within two years.
Revealing initial results from the trial to a Parliamentary Select Committee on assessment, Jim Knight, the minister for school standards, said that some secondary pupils might have been less motivated by the new tests. Some pupils also appeared to have been put in for the tests at higher levels than their teachers' assessment judgements suggested they had reached.
The new-style papers, in which children are faced immediately with problems of a given difficulty rather than tackling easier questions first, may also have put off some pupils.
Results in at least some subjects and levels have been disappointing. Full data will not be released until the autumn.
During questioning by MPs, Mr Knight said teachers and parents could be surveyed by the Government on their attitudes to testing.
Asked by Barry Sheerman, chair of the inquiry, why teachers were not being asked about the impact of testing, he said: "We could probably do some quantitative research with the teaching workforce around testing. I will certainly take that (suggestion) back to the department." He said that any study would also need to consult parents.