John Hynd, 16, received death threats after speaking out against the rising incidence of hate crime in Scotland, where the religious divide goes far beyond the Old Firm terraces

John Hynd has received death threats simply for joining a website campaigning against the sectarian divide in the west of Scotland. "I used to be a bigot," he says. "I'd go to the game – I'm a Rangers fan – and happily be singing Billy Boys along with my dad and his friends. Then I just thought, 'Hold on a minute. I've got Catholic friends. I'm going out with a Catholic. I don't want to be up to my knees in Fenian blood like the song says. I don't want this.'"

His stand has not only estranged him from his staunchly Protestant family but, after posting his phone number in a message on the site, he received calls from a man threatening to kill him. Hynd is only 16.

New figures released this weekend by the Scottish government show that religious hate crime in Scotland rose by 10% in the past year, with 60% committed by under-30s. A third of the charges related directly to football and 58% were against Catholics, 37% against Protestants.

On Tuesday the Edinburgh parliament will begin to debate controversial new legislation, nicknamed the "Football Act", which will give police more powers to clamp down on the sectarian chanting at matches that has landed both Rangers and Celtic in trouble with football's authorities this year.

On Monday two men will appear at Glasgow's high court accused of sending explosive devices to three people, including the Celtic manager, Neil Lennon, and to the Glasgow offices of Cairde Na h'Éireann (Friends of Ireland).

Defending one of the men is Donald Findlay, one of Scotland's leading lawyers, who had to resign as a director of Rangers after being filmed singing the sectarian song The Sash, and who has faced censure from his professional governing body over sectarianism.

The new crime statistics mean that almost 3,000 people have been charged with religiously-motivated crime since 2003. The Catholic church has described "entrenched hostility" to its members – 16% of Scotland's population.

Others have blamed the church for keeping Scotland's schools segregated along faith lines. But while the political debate rages, a grassroots fightback is quietly gaining traction.

At Hynd's school, Calderside Academy in Blantyre, a town eight miles south of central Glasgow, Yvonne Donald, 26, is showing him and his classmates a photograph of another 16-year-old, Mark Scott.

"Mark was walking home from a game, not an Old Firm game, at 5.15 in the afternoon," she tells them. He had tucked his Celtic scarf into his jacket as his mum had told him to. It wasn't enough to stop a group of Rangers fans heckling him. Then one of them cut his throat through to his spine in an unprovoked attack. The next picture is of Mark's white-faced schoolfriends carrying his coffin.

Mark's killer, Jason Campbell, now 37, who was released from jail this year, came from a family steeped in hatred – his father and uncle had both served prison sentences for their involvement in a Ulster Volunteer Force explosives conspiracy in Glasgow.

"This is a full-on example of sectarianism," says Donald, an education officer with the anti-sectarian charity Nil By Mouth. "For Mark it all ended because of that shirt." Nil By Mouth was founded by Mark Scott's friend Cara Henderson in 1999 as the only charity dedicated to fighting sectarianism. It almost closed due to lack of funding last year.

Its campaign director, David Scott, is optimistic, however, about the impact they can have. "Two centuries of sectarianism in Scotland and it took a 15-year-old schoolgirl to stand up to it. That's something and it is the young who will change this."

Scott talks to the class briefly before Donald asks if they think he is a Catholic or a Protestant. All hands go up for him being a Protestant. "He's just got that look about him," says one boy.

It's the kind of response that Alison Logan knows well. "You will ask children, what is a Catholic? What is a Protestant? And we've had answers like, 'A Catholic is ginger and aggressive,' and, 'Protestants are people who don't go to church,'" said Logan, social inclusion officer at Glasgow City Council's Sense Over Sectarianism project, aiming to unpick religious bigotry through twinning between denominational and non-denominational schools as well as drama and art workshops. "They are astonished when they go into each other's schools and find the classrooms look the same. Suddenly they realise they can be pals."

Football shirts feature in their work too. "We get them to try on the other team's shirt, and you do get situations where they'll say, 'I'm not wearing that,' with adults as well as kids. So it's about showing them it's just a shirt, showing them that when you're too busy screaming abuse at the other team's fans you've forgotten to support your own team."

Logan is optimistic about the future. "Teachers and parents are seeing a difference. When we started we were told sectarianism isn't a problem in Scotland; it's people like you stirring it up. It was a big taboo that we kept a lid on. Scotland remained one step behind in dealing with its bigotry, perhaps 10 years behind where we are with racism.

"Now there are debates happening up and down the country. There's guys talking about it in the pubs. We're having the conversation about the rights and wrongs. There's a real change. There's a real growing commitment, a groundswell of grassroots behaviour."

Hynd believes that his generation can bring change . "People that are spouting all this nonsense, they're just following their dad, who's following their grandfather, who's following his. Football is football. I love Rangers, but I'm not up to my knees in anyone's blood."