It is a bitterly cold Yorkshire morning and outside a school in Barnsley staff are involved in the most important part of the school day.

“All right, Kyle?” asks Dave Whitaker, the executive principal of Springwell special academy. “Morning, Kenzie. I saw some lovely writing of yours last night.”

One by one, the children are greeted by staff with a warm smile and a personalised hello. The teachers’ enthusiasm, however genuine, is rarely reciprocated. Some students scowl, others grunt a “hello”, almost all hunch their shoulders. One 11-year-old girl, Whitaker recalls, responded with a curt “Fuck off!” every single morning for a year.

That particular response would be met with instant isolation, detention or expulsion in many schools – but not at Springwell. “She was living in a house where there was violence, drug abuse, swearing – that was just commonplace and no one was nice to her,” Whitaker says. “So when she comes to us and we’re nice to her, she couldn’t cope with it.”

Instead of disciplining her, teachers paid the girl more positive attention in an attempt to understand the angst she was bringing from home. Within a year, she had stopped her morning outburst and got along with school staff. And that, the school’s principal, Verity Watts, explains, is why the daily greeting is essential: it allows teachers to spot which children are arriving in a foul mood. “You’re sussing out where the child is at and how they’re feeling,” she says.

Springwell is a special school for nearly 100 children, aged five to 16, with a range of social, mental and emotional health (SMEH) issues. Many have diagnosed anger-management problems, a lot are from “broken homes” or have attachment disorders. A depressingly large number of the pupils have suffered abuse, neglect or poverty before they arrive at Springwell. All have been deemed unsuitable for mainstream education.

But there is something else unusual about this gleaming new school. Its teachers vow to approach every child with what they call “unconditional positive regard” – or in Whitaker’s words, they “batter the children with kindness”.

It’s in sharp contrast to the “no excuses” approach used in a growing number of schools, which enforce a super-strict behaviour code, never mind the child’s individual story.

The concept of “unconditional positive regard”, which also seems to be growing in popularity – and in mainstream schools as well as special ones like Springwell – dates back to the 1950s and the work of the psychologist Carl Rogers, when it was applied to therapists and counsellors in the treatment of their patients. It means treating every human as equal instead of “saying someone is good only if they behave a certain way, or if they fit in certain boxes,” explains Professor Laura Winter, an expert in educational psychology at the University of Manchester.

At Springwell, Whitaker says, it means rewarding children for the smallest things - like being kind to fellow pupils - and not punishing bad behaviour. “I could have a kid that spits in my face today and tomorrow I’ll be OK with them,” he says. And if a pupils throws over a table and swears at the teacher? “The teacher would be really nice to them, talk nicely. It would be dealt with by the care team and that child would be looked after, taken out of the room for a calming period and then welcomed back into the classroom.”

Right on cue, an 11-year-old boy storms out of a classroom, shouting “fuck off!” as he tears off down the hallway, leaving an upturned table in his wake. The school’s care team barely bat an eyelid. The boy’s home life is complicated, they explain, and his behaviour has become more erratic. Luke Mitchell, the school’s head of behaviour, says the pupil would be taken to a quiet room filled with cushions and sensory lights to calm down, before being spoken to by staff and eventually returned to class. Throughout the school, the ambient notes of piano music are played to relax the students.

Mainstream schools are also finding success with this approach. At Passmores academy, best known for starring in Channel 4’s Educating Essex, Vic Goddard, the headteacher, says there is a commitment that no child will be left behind. In a system driven by exam results, Goddard says schools are increasingly at risk of abandoning the “naughty kid” as they focus all their attention on others.

“If a young person fails with English or maths, we put an intervention in place. We give them extra small group work, or an extra member of staff,” he says. “Whereas if they make a mistake with behaviour, we kick them out.” Not at Passmores. If a child kicks off at the start of every class, he adds, it is probably because they’re not getting attention in any other aspect of their life. Instead of ostracising that pupil for being disruptive, Goddard says they should be “given as much attention as they want right at the start of the class” to satisfy the child’s emotional needs. Instead of a school behaviour policy, Passmores has a “relationship charter” that “seeks to affirm rather than condemn, to reward as well as challenge”. There are sanctions, starting with a student being spoken to and a “restorative justice experience”, but permanent exclusion is deemed a “drastic and unwanted penalty” used in only extreme cases.

Crista Hazell, a teacher in a mainstream secondary school in the south-west of England, found the approach worked with a “really quite challenging” French class when she simply stopped telling them off for failing to bring their pens, pencil or books into her lesson. “I will challenge them on things if they are taking the mickey, I’m not a doormat,” she says. “But confrontation is something that doesn’t happen now. Kids don’t learn from teachers they don’t like, do they? We could be the first person that says something positive to them that day, or that week, depending on what their home circumstances are.”

It is the zero-tolerance schools that more often hit the headlines. The Great Yarmouth Charter academy, for example, where students must be punished if they fail to smile and thank their teacher after class. Or the Michaela school in north London, where detentions are given for forgetting a ruler, or for turning round in class. Others, such as the Gorse Academy Trust in Leeds, espouse a “positive discipline” approach based on rewards for good behaviour and “really harsh” punishments for indiscretions.

Where does Tom Bennett, the government’s behaviour tsar, sit on the debate? In a report for the government last March, Bennett said there was a national problem with pupil behaviour, in part because teachers believed telling students what to do was “oppressive”. Speaking to the Guardian, Bennett says he is “very, very for” unconditional positive regard but that it is essential that pupils are taught self-discipline: “There are certain things all schools need to do to have good behaviour - have high expectations, consistency - but how those themes are enacted in a school are often incredibly contextual.”

The way Michaela uses unconditional positive regard, he adds, is by being “absolutely on the pupils for micro-behaviours”. “I think unconditional positive regard can be understood in lots of different ways.”

Back at Springwell, the children are being “settled in” before beginning their lessons. For Key Stage 1 pupils, this means five minutes of yoga and quiet play. Older children munch toast and listen to a story, or watch Mr Bean’s Holiday on a projector fastened to the wall. At 11am, the children gather for a weekly singing assembly. This week they sing the Friends theme song, I’ll Be There for You, as music teacher Maria Roberts plays along on the piano. When it was first introduced, the singalong rapidly descended into a chaotic frenzy of “kicking-off and throwing chairs,” says a teacher on the sidelines. Today, at least, the children behave impeccably.

In his sparse office, Whitaker bristles at the suggestion his school has no rules. Some of the indiscretions that go unpunished at Springwell might merit isolation or worse elsewhere, he says, describing the zero-tolerance approach as “barbaric”. “Those systems of rigid consistency, with no flexibility, I think it is verging on bullying.”

Goddard says every school is entitled to take its own approach to pupil behaviour. He fears, however, that disciplinarian schools are “consigning certain children to the dumpster” by refusing to address their needs. “Taken to the nth degree, zero-tolerance means there’s no capacity for children to make mistakes and if they are making mistakes they’re removed,” he says. “The potential for long-term damage for that removed child is massive.”