They took part in a Schools Mass, which was celebrated by Bishop Alan Hopes, and organised by the seven schools from Cambridgeshire and Peterborough, and then enjoyed a huge picnic in the cathedral gardens next to the Narthex centre.
Sean Hayes, Headteacher at St John Fisher High School, Peterborough, said: "The theme was Children of God with the intention that it is very much a children's Mass with them doing the readings prayers and singing.
"For a lot of pupils they take away the experience of coming to the cathedral, to see the Bishop in his cathedral seat and to understand that they are part of a larger diocese. It is just a great time to all come together."
In his homily, Bishop Alan said: "The day of our Baptism is the most significant and important day in our lives, because it is the beginning of a very special friendship we have with God that will last for the whole of our lives and continue after we die.
"Through our Baptism we also become children of God ' brothers and sisters of Jesus Christ ' an awesome claim. We also become members of God's worldwide family – the church.
"If we are faithful to our friendship with God it will help us to live beautiful lives without selfishness, it gives us purpose in life and we can make such a difference to the world in which we live."
Each school present received a special plaque of the diocesan crest from Bishop Alan to take back to school as a memento of the occasion.
Click here or see below for a full picture gallery of the Mass. Pictures are free to download.