Riverside County prosecutors say both teens made the admission in juvenile court.
The defendants previously faced charges of voluntary manslaughter in the death of 13-year old Diego Stolz, a student at Landmark Middle School.
Teen suspect in fatal Moreno Valley school fight faces judge
A bystander's cellphone video shows Diego being punched and then falling and hitting his head on a pillar during an on-campus altercation last year.
Both of the 14-year-old juveniles are expected to be sentenced in February.
They have not been publicly identified because they are minors.