Three times as many checks are to be carried out on the marking of key stage 3 English tests this year, the Edexcel exam board said this week.
On-screen marking could be introduced for the tests next year, it was also revealed.
The extra checks come after repeated warnings from ministers to the Qualifications and Curriculum Authority last year about the quality of marking of tests for KS 2 and 3 English.
Edexcel, which took over the running of the tests this year, hopes the measures will avoid complaints of erratic marking and delays of up to three months in returning scripts.
In an attempt to rebuild confidence in the tests, The TES was also invited to observe marker training in action for the first time.
Fears that the target number of markers would not be reached proved unfounded, after 2,000 signed up for the pound;1,000 job.
But at the training session in the ExCeL centre in Docklands, London, there were signs that some had been recruited at the last minute, as several had not received any preparation materials.
Team leaders' main task seemed to be to encourage markers to be more generous to scripts, as most tended to underestimate the scores. But they seemed confident that the mistakes of last year would be avoided.
Other safeguards include ensuring that half of each school's scripts are marked by one marker, and half by a second. Results can then be compared and any differences investigated. A quality assurance centre will also be in place, carrying out statistical analysis, checking for anomalies with past results and predicted scores.
Gary Ward, Edexcel spokesman, said: "A single script could potentially have five or six checks carried out on it."
English marks will therefore not come out until GCSE results day on August 25 rather than the end of summer term.
The QCA said the possible introduction of on-screen marking next year would allow for rapid feedback between markers and team leaders and slash the marking time.
Shaun Willis, from Torr Point community school, near Plymouth, is a new teacher who marked for the first time last year and is now a team leader.
The 26-year-old said he had no hesitation about signing up for another year.
"I wanted to think about my own teaching and thought marking would make it so much better," he said.
But he admitted that some markers had felt they were unfairly criticised after the problems last year.