The Liberation Tigers of Tamil Eelam (LTTE) said members of their eastern units had taken the children away on Monday night in Ampara district.
"It was a mistake by the field commanders, but we are taking strict disciplinary action against our own people involved in this," LTTE military spokesman Rasiah Ilanthiriyan said when contacted by telephone.
He said the LTTE had already suspended the field commanders who had carried out the kidnappings.
Ilanthiriyan's remarks came after the defence ministry accused the Tigers of taking the students and teachers to a military training facility in the eastern province.
The youngsters, who were attending a night tuition class, were taken to an LTTE training camp at Kanjikudichchiaru, the ministry said in a statement.
"The devastated parents of the abducted children have made a complaint to the Sri Lanka Monitoring Mission (SLMM) and have afterwards left ... in search of their children," the statement said.
Norwegian-led monitors said the