Tom Riordan, chief executive of Leeds City Council said:
"We are aware of the serious incident at Corpus Christi Catholic College this morning and our thoughts are with all those concerned.
"We are working with the school to support pupils and staff at this very upsetting time. We wish to reassure people that this was an isolated incident and there is no ongoing risk to pupils or staff at the school.
"We are working closely with the police and helping with their investigation."
A spokesman for the Diocese of Leeds added:
"The thoughts of all of the Diocese are with the families involved – all is being done to give support to all those involved"
The Catholic Education Service said:
"Our thoughts and prayers are with the community of Corpus Christi Catholic College at this sad time."