A TEACHER who was sacked for misconduct including putting a student in a headlock after the youth punched him said the NSW education system left teachers "powerless to discipline kids".

Science and agriculture teacher Stephen Krix was fired from Riverstone High School when he fought back against a year-10 student who refused to work and punched him in the face during a class.

Mr Krix - a "squarely built" 51-year-old who had worked in various public and private teaching roles since 1989 - told The Sunday Telegraph he acted in self-defence when he put the "slight" student in a headlock during a science class in May 2011.

The incident came after the student refused to take off his headphones, told Mr Krix to f*** off several times and punched the teacher when he stood close to him with a worksheet and refused to move.

The incident was outlined in the NSW Industrial Relations Commission last Wednesday where Mr Krix lost an appeal against the sacking he claimed was "harsh, unreasonable and unjust".

In an interview with The Sunday Telegraph, Mr Krix, who now works in the security industry, said the public system was failing kids because teachers feared being sacked if they disciplined students.

He said students were leaving public schools without the self-restraint required to cope with post-school life.

"It's a joke - that's why people are running to private schools," Mr Krix said.

"Eighty per cent of kids are screwed over by the state system because of a lack of discipline given to a minority of bad kids who disrupt classes," he said.

"You have to have zero tolerance … if a kid is behaving badly in the classroom he needs to be extracted and all the kids that are behaving themselves need to be able to get educated."

In relation to the student, Mr Krix said: "It's not like he's some sort of pathological killer … he's just a kid who needed discipline and wasn't getting it. If he's given the guidelines then he knows where the boundary is".

A NSW Department of Education and Communities representative told the commission Mr Krix should have stood down from any physical confrontation.

The representative said the Teaching Service Act meant that teachers had to respond to situations with the safety of students being the top priority.

media_camera Mr Krix was told he should have stood down from any physical confrontation..

The commission heard Mr Krix was in trouble for other incidents including one where the he caused three year seven boys to fall over when he blocked their path as they ran out of his classroom. The boys were from another class.

The 51-year-old had been "told by his head teacher … that `teachers cannot block classroom doorways and they should not obstruct students trying to leave the class' even if there were a disciplinary issue involved", the commission heard.

Another incident saw a year seven student receive "serious burns" and two others were set on fire in a science experiment led by Krix where students started kicking flammable liquid at each other.

The experiment involved Mr Krix lighting petrol in a "science pneumatic trough" in an outdoor area.

But the teacher left the students alone at scene of the experiment when he saw another student trying to "take a can of fuel" from the back of his ute.

While he was away, other students "were kicking at the pots of flaming liquid … until one boy kicked the pot over" and the flaming liquid spilt on three boys, the commission heard.

"20-20 hindsight is a marvellous thing," Mr Krix said. "If I was doing it today I wouldn't have the ute where it was … but I thought they'd have enough sense not to kick flammable liquid at each other."

media_camera Stephen Krix fought back against a year-10 student who refused to work and punched him in the face during a class.

IRC commission Peter Newall said it was a "gross failing" of Mr Krix to turn his back on the students standing around "flaming petrol".

Of the headlock incident, Mr Newall told the commission Mr Krix "did not need to do so".

"…Mr Krix no doubt very understandably irritated by a student who refused to work, who distracted others and who swore when told to do some work, got in (the student's) face," he said.

"He could have withdrawn from physical engagement with the student and did not."

Mr Newall noted that "teaching in the modern classroom" can be a "taxing and difficult job".

"That teachers can expect to be sworn at and at times physically attacked must make the requirement to maintain calmness, patience and a disciplined learning environment extremely difficult."

he commission heard Mr Krix had a "substantial body of achievement, largely in the independent school system" but also in voluntary work including a "training long term unemployed and ex-prisoners".

He also taught in a program in Blacktown and Mount Druitt where kids who had been barred from schools could get the equivalent of their school certificate.

A NSW Department of Education and Training spokesman said its policies and procedures state clearly that disciplinary action will not be taken against teachers who act reasonably in their conduct while disciplining students.