He would have been open to prosecution if he had been a year older - but as a 13-year-old cannot yet be held criminally responsible for his actions under the Spanish penal code.
Police in the south-east city of Murcia where Wednesday morning’s incident happened confirmed the youngster was spoken to in the presence of adults thought to be his parents but was not formally arrested because of his age.
A prosecution source said: “Spanish law exempts children who are younger than 14 from criminal responsibility.”
Confirmation the teenager would face no charges came as details began to emerge about the 41-year-old Irishman at the centre of the stabbing drama at private all-boys’ school Colegio Monteagudo in Murcia.
He has been named locally only as Paul K and described as a father-of-two who is married to a local woman and has lived in the area for around a decade.
He was taken to hospital with a small stab wound but is understood to be back at home after being admitted for observation to the Morales Messeguer University Hospital in Murcia as a precautionary measure.
A friend and former teacher at the school, run by Catholic Church organisation Opus Dei, told Spanish news website El Español: “Paul has lived in Murcia for around 10 years and teaches English and Technology.
“He’s a brilliant teacher. He’s never spoken badly to a pupil or had any problems because he’s an excellent professional who’s adapted well since he emigrated from Ireland.
The unnamed pal added: “There were no previous problems between Paul and the pupil. No-one can understand what has happened here.”
Reports yesterday/on Wednesday said the Irishman had been stabbed three times with a knife the teenager taken away by police is understood to have shown to a classmate in the toilets before allegedly going on the attack as Paul turned his back to pupils during a morning class to write something on the chalkboard.
One unconfirmed local report said he had told the classmate as he showed him the weapon: “I’m going to cause a stir.”
The alarm was raised around 10.45am.
A spokesman for a central government-run emergency services coordination centre confirmed after the drama: “We received the alert at 10.44am on Wednesday morning.
“The caller said a teacher had been attacked from behind by a pupil with a sharp object.
“National and local police were mobilised along with an emergency response ambulance to attend to the injured teacher.
“He was assisted at the scene before being taken to Morales Messeguer University Hospital in Murcia.”
The pupil at the centre of the drama had been at Monteagudo School for nearly two years after transferring from a private school in nearby El Palmar which has been named in Spanish press at El Limonar International School.
He was described on Thursday by a local education source as a “normal boy” whose behaviour before Wednesday’s incident had not been a source of concern.
His parents are said to have apologised to school chiefs and are now expected to be interviewed along with their child so the school can take a decision on whether he continues as a pupil there and what internal punishment he should face.
The regional council has put psychologists on standby so they can speak to both the teacher and the student.
Although the teenager will not face criminal prosecution, police confirmed on Thursday his parents could face a civil compensation claim from the teacher for their son’s actions.
The Spanish National Police source said: “There’s no criminal responsibility here but there is a civil responsibility which will fall on the parents in this case.
“Here police have acted from a position of protection in line with Spanish legislation concerning minors of this age, both towards the youngster and the teacher.
“After the initial police response with officers being sent to the scene, a specialist Judicial Police Juvenile Group called the Grume was mobilised to protect the youngster and guard him.
“They contacted the boys’ parents and alerted youth prosecutors. He wasn’t arrested and nor was he formally interviewed but spoken to in the presence of his parents for a report that will be made available to the relevant authorities.”
“The object of the exploration as we call it would have touched on the incident that occurred and an inquiry into his life and how he gets on with his colleagues and friends and what his family surroundings are, to be able to pass on information to youth prosecutors.”
The teacher’s whereabouts on Thursday was unclear although he was thought to be resting at home.
The school has said it is “very sorry” about what happened.
It also confirmed the teacher was “out of danger” in a statement released yesterday/on Wednesday and said it was confident he would make a “full recovery.”
Monteagudo School said in its short statement released to the press: “We are very sorry about what happened.
“We work daily at the school so that our pupils develop in a climate of respect and good co-existence.”
Mabel Campuzano, regional government director of education, admitted the incident had initially sparked “chaos" with reports of up to five officers hauling the boy pupil away after he ran out of class following the stabbing incident and took refuge in a secretary's office.
But she also confirmed the teacher was “doing quite well” and had no serious injuries.
The general age of criminal responsibility in Ireland is 12 but there is also provision for children aged 10 and 11 to be criminally tried for murder, manslaughter, rape or aggravated sexual assault.
Where a child under the age of 14 years is charged with a criminal offence, no further proceedings can be taken without the consent of the Director of Public Prosecutions.