Two boys were taken to hospital where they were treated for injuries. A third boy was uninjured but shaken.
Rotorua Boys' High School would not reply to questions from the Rotorua Daily Post about whether Simpkins had been stood down or what his guilty plea meant for his role.
However principal Chris Grinter issued a written statement saying:
"At this point in time the school and the Board [of Trustees] have taken advice and are following due process relative to this matter. The matter will also be discussed at this week's meeting of the Board of Trustees.
"It is not appropriate to make further comment relative to your various questions at this point in time."
The Education Council said it would not become involved as Simpkins was not a qualified teacher.
But in response to questions, the Ministry of Education said any organisation funded by the government must observe the provisions of the Vulnerable Children Act.
A police vet must be obtained for anyone appointed to work during normal opening hours.
"Under Part 3 of the Vulnerable Children Act 2014, all children's workers must be police vetted as part of a safety check.
"A children's worker is anyone whose work involves regular or overnight contact with children, takes place without parents or guardians being present, and is paid or undertaken as part of an educational or training course. A police vet must be obtained before the children's worker starts work," its website states.