Charles Aranguiz has just scored what will be Chile’s winning goal against world champions Spain and in the São Paulo Fan Fest, Olavo and his friends cannot believe it.

They may be Brazilian kids from a favela near the new World Cup stadium in Itaquera and support their local team Corinthians, but with their Real Madrid and Barcelona shirts and sweatpants, it is Spanish football that they seem to admire more than their own.

“Brazil is OK,” says Olavo, 17, with a shrug. Neymar gets a thumbs-up, but Spain, he says, play “beautiful” and the names of Xavi, Iniesta, Alonso and other Spanish stars roll quickly off his tongue. Today, though, he can only shake his head in disbelief.

Our meeting with Olavo, Lucas, and Fernando, who range in age from 12 to 17, proves the old adage that football truly is a universal language. Waiting in line with my son to play Fifa World Cup at the Sony stand in the Fan Fest, they are soon curious to find out where we are from and what football teams we support.

Using Google Translate on Olavo’s Galaxy phone, they talk to us about music, ask how hot the girls are in Bermuda (a place they had never heard of) and tell us a little about life in their favela. They like “funk”, which seems to be Brazilian hip-hop, and Olavo seems to be quite the performer. He shows us videos of him rapping from rooftops in the favela and photographs of him performing in front of sizeable local club audiences.

Life in the favela is clearly tough. “It is very dangerous,” he says. “People they want to rob your cell phone, they steal from children.”

He points to his shoulder and lower leg, where he says he has been stabbed at various times in his young life.

They warn us that around the Centro, the heart of downtown São Paulo where the Fan Fest is situated, we should be careful — especially of a trick where someone will distract an unsuspecting tourist by almost running into you on a bicycle while his partner in crime slips off your watch, jewellery or relieves you of your wallet.

We thank them for the advice but also wonder if they may be adept at similar tricks themselves. When they later offer to give us a guided tour of the area, we politely decline, sensing that we may be pushing our luck a little too far, especially on our first full day in Brazil.

That may be unfair but, sadly, you simply cannot be too careful here. The omnipresent and menacingly armed military police and heavily barred shops, hotels and homes remind you that crime is a fact of life. Even when we collected our match tickets from the Fifa Ticketing Centre, we were warned to keep them well hidden as we left the building.

I watch my son Toby and Fernando do battle as Cameroon and Brazil on the PlayStation, laughing and as animated as if they were on our couch at home, even though neither understands a word of what the other is saying, beyond “gol” or “penalty”. Despite a world of difference, they have found a connection through a love of football.

There is great joy in watching kids just be kids and, as we leave the Fan Fest and bid the boys tchau, I wonder how much of the innocence of childhood has already been taken from them by the harsh realities of favela life in São Paulo.

And I hope they get to stay kids just a bit longer.