Thousands of 14-year-olds have finished this term without receiving their English national test results after a series of bungled changes led to a marking “fiasco”.

Staff jammed the switchboards of test administrators trying to find out why scores for the tests, taken by 600,000 pupils, had failed to arrive in the post.

Those who tried a website said to list the scores found it had either crashed or had incomplete or inaccurate information.

Today is the deadline for schools to appeal against any disputed results.

Parents are supposed to be given results by the end of term.

The problems stem from changes aimed at improving marking by letting examiners focus on either reading or writing papers.

Instead the changes have created huge headaches at secondaries about to break up for summer. Some complain that candidates were given zero for long written answers, while other scripts arrived with pupils’ scores incorrectly added up.

This week, the National Assessment Agency, the new body set up to run England’s testing system, apologised for the delays.

The tests carry extra political significance this year, as they are the first taken by pupils educated for all three years under the key stage 3 strategy to boost attainment. One local-authority adviser said: “This is the most chaotic I have ever known the tests to be. How can the Government be sure that these results will be a proper measure of the success of the strategy?”

In January, schools were told that the marking changes meant that they would not receive results till July 13, a week late.

But this was only the beginning of the problems. Computer glitches meant markers were not able to do vital checks on all scripts. Many schools failed to get their results by last Tuesday’s deadline. When they tried to find out the scores on a website, it crashed or had inaccurate information.

Catherine Davidson, head of English at Hull Trinity House school in Hull, said the Qualifications and Curriculum Authority website contained only a third of her results.

She said: “We had to sit down and work out the results by ourselves with the scripts. We soon found there were clerical errors.”

Michelle Keown, head of English at Kingsmead school, Enfield, north London, who had to come in to check scripts after term finished this week, said: “I don’t know why I should have to come in during the holidays.”

Teachers are unsure whom to blame: the National Assessment Agency; the AQA exam board, which runs marking, or the Data Collection Agency, owned by the Pearson publishing group, which collates the results. From next year, Pearson, which also owns the Edexcel exam board, will run KS2 and 3 tests after winning an pound;80 million contract.

Jackie Bawden, director of national tests at the assessment agency, said:

“The changes were brought in to improve the quality of marking and provide more information for schools on KS3 English. But it has taken longer (getting results to schools). For this we apologise profusely.”

The QCA said that 170 schools had not received results by the end of last week.