It has taken two years, a sustained lobbying campaign and an exhausting round of letter writing for Liz Webster to get some justice for her 17-year-old son.

In January Mrs Webster, 44, met schools secretary Ed Balls, who recommended an inquiry into the savage attack, on school premises, on Henry Webster by a group of Asian teenagers.

It was January 11, 2007, when Henry, then 15 and a ginger-haired star rugby player, popular with his class mates and with no history of being disciplined for poor behaviour, arrived at the tennis court at The Ridgeway School in Swindon to settle, "one on one", an argument with a fellow pupil. Only it was a baying mob and not a single opponent waiting for him.

What happened next, witnessed by more than 100 pupils – and even filmed by one on a mobile phone – was an ambush so vicious that, at the subsequent court case, the judge described it as a ''savage and sustained attack".

It was, said Judge Carol Hagen when she passed sentence on 13 boys and young men who set upon Henry, a ''miracle'' that Henry had survived.

Though the 13 Asian teenagers and young men who attacked Henry – all members of a gang who called themselves the ''Asian Invaders'' – were given sentences of between eight months and eight years for grievous bodily harm and conspiracy to commit GBH, no independent inquiry into how Henry was brutally assaulted, while at school, in an attack that was described in court as ''something out of a Quentin Tarantino film".

During the trial, Judge Hagen was highly critical of the school, asking why there were no staff present in the tennis courts at the end of the school day, since it was known there had been trouble earlier in the day.

For the past 14 months Henry's mother has battled for a full inquiry and, after gaining support from the Government, has now won the right to a Serious Case Review on the attack.

The inquiry, which does not seek to apportion blame but to investigate what happened and evaluate what lessons can be learned, is expected to last four months and will, for the first time, lift the lid on alleged racial tensions within a school.

''I've fought hard to find out all the facts,'' said Mrs Webster, who is also suing The Ridgeway School for neglect. ''And it's been an excruciating wait.

"The school might say otherwise but the fact is that the attack on my son was a racial one. The school knew there were tensions – there have been numerous similar attacks before but nothing was ever done.

"Everything was swept under the carpet. Neither Henry or I am racist. But I feel my son was badly failed by a school that believes racism is only ever something that is carried out by white pupils."

It took a sustained campaign before the review was instigated by Mr Balls, the Secretary of State for Children, Schools and Families.

After a meeting with Mrs Webster he wrote to her saying that it was ''unacceptable that there has not been any full investigation of such a serious incident which left your son with permanent injuries".

Henry was repeatedly kicked, punched and battered before being beaten on the head with a claw hammer, fracturing his skull in three places and leaving him with permanent brain damage.

The Swindon local authority referred the case to their Local Safeguarding of Children Board, which has now sanctioned the review.

The headteacher of The Ridgeway School, Mr Steven Colledge, has said that he welcomes the investigation.

The case has highlighted the extent of racist incidents in our schools and, in particular, the reluctance on the part of some to treat attacks as racist when they are carried out by minority cultures.

Mrs Webster was not aware that, when those who carried out the crime came to court, it was up to the prosecution to cite the attack as racist.

Had that been proved, the sentences meted out – especially to Wasif Khan, 19, described in court as ''the hammer man'' and who was jailed for eight years for wielding the weapon that fractured Henry's skull – may well have been much stiffer.

What is particularly worrying, however, for parents in Swindon, is the light the case has shed on the number of racists attacks in the city's schools and how such incidents escalate.

Between November 2006 and November 2008 police dealt with 337 crimes – 137 of them violent incidents – at Swindon schools.

The highest number of those attacks, some 58, occurred at Churchfields school while 52 were recorded at Ridgeway school.

In the past 12 months, admittedly, perimeter fences and bans on mobile phones has helped the school reduce its number of violent crimes.

Henry, bleeding heavily from his head, was taken to hospital and, within 35 minutes, police had rounded up several of the gang members. It was Joe, Henry's younger brother, who telephoned his mother.

He had been standing at a bus stop when a passing pupil told him Henry had been beaten up. ''You can't imagine how it feels to see your son soaked in blood,'' Mrs Webster said, tears threatening.

''I just couldn't believe that no one from the school had called me to say there had been trouble earlier. All the pupils knew something was going on.

"When I was with Henry at the local hospital's accident and emergency unit one of Henry's friends telephoned me to say the same thing had happened to him some time before but he had managed to get away.

"All the children knew that these 'Asian invaders' were terrorising white pupils.''

For Mrs Webster the Serious Case Review will, she hopes, give some insight into how such a violent attack happened on the school premises.

''As far as I can see there was no control and no discipline,'' she says. ''Bullying and violence were rife when Henry was attacked and I want the school to admit that.''

Mr Colledge, the headteacher of The Ridgeway School, was unavailable for comment.