The Kenya National Examinations Council (Knec) has cancelled the results of 3,427 KCSE candidates at 44 centres because of cheating.
Chairman George Magoha made the announcement on Tuesday, noting investigations were thorough.
Mr Magoha noted that the cancellation was painful for the students.
Representatives from their schools and local education officials were briefed on Monday and Tuesday on the findings of the probe, he said.
“The investigations showed that the malpractices took place due to negligence and commission or omission of contracted professionals who did not perform their roles as per the guidelines for management of examination,” he told the press at Knec headquarters in Nairobi.
The chair said, however, that those whose results were revoked can register for the 2019 Kenya Certificate of Secondary Education tests.
The registration deadline for the year's examinations is February 15.
“[They can register afresh] instead of having to wait for three years as provided for in law,” said the chairman who was accompanied by Knec Chief Executive Officer Mercy Karogo and other board members.
Mr Magoha further announced that 1,275 candidates at nine centres were cleared from allegations of cheating so they will receive their results.
The results from 53 centres in 16 counties were withheld over the same claims.
"Knec conducted thorough, fair and objective investigations into the cheating allegations to ensure findings were credible and verifiable," Mr Magoha noted.
"A few cases of reported malpractices were handled during administration of the examinations and preventive action put in place," he added.