By Mark Lowen
BBC News, Stolac
Zeljka Raguz calls the Croatian conflict "the war for our homeland"
Geography teacher Zeljka Raguz begins an impromptu test for her final-year students.
The high school is in southern Bosnia, but her questions have a rather different geographical focus.
"What are the main cities in Croatia?" she asks.
"Which European country has the largest Croatian community? Are there many Croats in Africa?"
She calls the Croatian war of the 1990s "the war for our homeland".
The dozen or so students in the class at Stolac High School are Bosnian Croats, who learn the Croatian curriculum and attend school in the morning.
Bosniaks - Bosnian Muslims - are taught on their own at the same school, but in an afternoon shift.
The system, known as "two schools under one roof" was introduced in 2003, replacing a previous set-up in which different ethnic groups were often taught in separate establishments.
Intended only as a temporary measure, it was an attempt to allow families who returned after the war to educate their children in proper facilities.
But more than 50 schools in Bosnia remain divided today.
The parliament of the Bosniak-Croat Federation - one of the two semi-autonomous entities making up post-war Bosnia, and the part where the Bosniaks are concentrated - recently adopted a resolution to establish multi-ethnic schools.
But many local municipal authorities are unwilling to make the change.
"It's not good for our future, but that's how it is," says Marija Blatnjak, an 18-year-old Bosnian Croat student.
"You can see that the different students don't communicate," she says. "That will be a big problem for our country because we learn to be separated."
As the Croat shift ends, a bell signals when the waiting Bosniak students can enter the building.
They pass under a Croatian flag, which hangs over the doorway. Eighteen-year-old Bosniak Emin Isakovic tells me he, too, has reservations about the system.
"If we were together at school, we'd be able to understand and get to know each other," he says.
"As it is, we can't form our own opinions about others. We have to solve the school separation issue before we can start to tackle other problems here."
At the adjoining elementary school, the separation is even more marked.
Children there use different parts of the building, according to their ethnic group.
A Croatian flag hangs over the entrance of the Stolac school
To enter the school, the Bosniak pupils walk past the Croat section, through a set of gates towards their own separate door.
Fifteen years after the Bosnian war, which tore apart ethnic Croats, Bosniaks and Serbs, critics say the ongoing school separation is sowing dangerous seeds.
"It's educational apartheid," says local human rights activist Nerin Dizdar.
"The young are taught that the other one is a threat to them. It generates ignorance and hatred and these are the main ingredients for future conflicts."
There is some support for the status quo among the students.
One boy told me that, since Croats and Muslims clashed so badly during the war, it was better to keep them separate at school to avoid any unwanted consequences.
"This is the only possible education system now", says Croat head teacher Mirjana Biletic.
"The shifts are only there for logistical reasons - not for segregation or discrimination."
Asked why a Croatian flag hangs at the entrance to a Bosnian school, she says: "If students have a problem with that, they can lodge a complaint through the official procedure."
Just 30km (19 miles) away in the city of Mostar, the brightly-coloured high school provides a very different educational experience.
Croats and Bosniaks are still taught their own curricula, but they go to school together and enjoy mixed activities in the library or sports hall.
It is the only former "two schools under one roof" institution in the country to have been united.
"I like how everyone is together", says 15-year-old Andrea Bevanda. "That's how it's supposed to be."
"Kids in this school are more tolerant", she says, when asked whether her friends behave differently to those in other, still-divided schools.
"They're kind to one another. They hang out together."
Kenan Ridjesic, a Bosniak teenager, agrees.
"I have a lot of Croat friends," he says. "The good thing about this school is that I don't see the difference between us. We're all humans - blood, flesh, bones. They just go to church and I go to the mosque."
Bosnia is still trying to move on from its devastating conflict, to rebuild the multi-ethnic harmony it once had.
But many believe these attempts will be thwarted unless the educational system is reformed - unless the next generation of Bosnians learn how to coexist peacefully.
"If we don't change our way of life our kids will be the same," says Luca Aleksic, an 18-year-old at the Stolac school.
"People here think it's wrong to mix with boys from the other culture. If you go to a cafe together, they say you're stupid, you're different," she says.
"But I think we should be grateful to have other friends. This is one country and we could be better."