Thousands of teenagers were punished for cheating in their GCSE and A-level exams last year, figures showed.
The Government watchdog said 4,258 candidates were caught, with a quarter punished for taking mobile phones or other gadgets into their exams.
At the same time, the number of teenagers given extra marks for being ill on the day of their exams rose sharply, the Qualifications and Curriculum Authority (QCA) said.
In a report on the 2007 exams, the QCA said 1,620 pupils were warned, disqualified or lost marks for introducing "unauthorised material" into the exam hall.
The watchdog went on: "Within this category, around two-thirds of cases related to mobile phones or other electronic communication devices. Almost one-third of the candidates penalised for malpractice were penalised for plagiarism, failure to acknowledge sources, copying from other candidates or collusion."
The QCA also warned of a significant rise in the numbers of candidates asking for special arrangements to be made to accommodate their needs in exams. These included having extra time, help with reading and the use of computers to complete answers.
Last year, exam boards received more than 470,000 requests for such special access arrangements to be made. Exam board officials approved arrangements in 150,000 cases, a 20% rise on 2006 and up from 105,000 in 2005. And the boards approved 308,000 requests to give extra marks to candidates who were absent or "disadvantaged as a result of temporary illness, injury, indisposition or other unforeseen incidents".
QCA chief executive Ken Boston said there was a need for "vigilance" after the number of candidates with special access arrangements "increased significantly".
"This may be due to an increasingly professionalised body of exam officers who work hard to ensure that candidates get the access they are entitled to," he said. "But we need to monitor the situation closely to ensure that the system remains fair for all learners."
:: The National Assessment Agency (NAA) confirmed a rise in the number of cases of cheating in primary school tests. League tables last year showed official inquiries at five schools in England uncovered malpractice in the national curriculum "Sats" tests taken by 11-year-olds.
