The 16-year-old schoolboy from Tynan collapsed on Tuesday and died several hours later.
School principal David Livingstone said both staff and pupils “have experienced shock and disbelief” as a result of the tragedy and that “our hearts go out” to John’s family.
“The Irwin family has a long association with City of Armagh High School and John’s mother, Diane, is a member of the Board of Governors,” he said.
“John was a popular young man and was held in the highest regard by his teachers and fellow pupils alike. He will be greatly missed by all, particularly those within his form class. John possessed many fine qualities. Since his passing words which have been used to describe him include patient, kind, courteous and polite.
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“He always saw the good in others and was keen to help and support those who were in difficulty. He worked extremely hard at every task he undertook. His qualities led to John being appointed Prefect, a role which he approached with enthusiasm. John was actively involved in making plans for his future, hoping to pursue a career in butchery alongside his farming activities.”
“His outstanding good nature and determination will always be remembered. It was indeed a privilege to have him as one of our pupils; all our lives have been enriched by knowing him.”
John funeral will take place from the family home at Coolkill Road, Tynan on Saturday at 1.30pm to St John’ Parish Church, Middletown.