Bullets in the classroom: Cameroon students caught in Boko Haram crossfire

Their insides cramped with fear, pupils' eyes dart from their teacher towards the windows during class, unable to concentrate on their lessons.

"We have a phobia, the danger is always there," said Boris Bouba, a 20-year-old student at the school.

"When we are in class, we are always keeping watch on the windows. We can never fully concentrate because we are afraid."

As the school year wraps up, pupils gathering in the tree-lined courtyard appear impatient to get their reports and leave as soon as possible.

"We are always on the alert," school headmaster Jean Felix Nyioto told AFP, seated behind his desk in a cramped office.

"At any moment gunfire crackles on the other side, but also from time to time here" in Fotokol.

The other side refers to Gamboru, a Nigerian village descended upon by swarms of Boko Haram fighters in May. The extremists opened fire on residents in an attack which local sources say left at least 300 people dead.

The Fotokol highschool is just 300 metres (nearly 1,000 feet) away from Gamboru, separated by only a small river.

However there is no fence or security for the nearly 600 uniformed youngsters who file into its classrooms every day.

- Threats to burn down school -

His expression taut, Nyioto describes how bullets from Gamboru regularly zing through the highschool, and mortar shells fall nearby.

However the headmaster is currently more anxious about flyers that recently appeared on the streets of Fotokol, threatening direct attacks on the school and its teachers.

"Boko Haram has threatened to burn down the school, customs and government buildings. We are so scared of being targeted," said another student, Ali Abba.

Boko Haram, which has been waging a violent insurgency in Nigeria's north since 2009, loosely translates as "Western education is forbidden".

The hardline Islamists have burned down many schools, often massacring students in their sleep. In February nearly 60 Nigerian pupils were killed in an attack on their dormitory before it was razed to the ground.

Their deadly insurgency hit international headlines in April when 219 schoolgirls were taken hostage in the remote northeastern town of Chibok.

Cameroon, which shares 2,000 kilometres (1,250 miles) of border with Nigeria, is increasingly targeted by Boko Haram. The Islamist militants have already kidnapped several foreigners there.

In mid-May suspected gunmen from the group took 10 Chinese road workers captive in an attack which left a Cameroonian soldier dead.

- Kidnapping terror -

The girls at Fotokol highschool are particularly afraid of what Boko Haram may have in store for them.

"I am so scared Boko Haram will come to our school and kidnap us," said Sidonie Dimissigue, 15, a Christian who says she has been wracked with anxiety and unable to concentrate in class since hearing of the Chibok attack.

"Thoughts are racing through my head. I speak to Daddy about them to try and calm down," she said.

Alice Kouvou, 20, said she decided to stay in school despite efforts by her parents to get her to leave Fotokol.

She is afraid the kidnapping of the Nigerian girls will "radicalise Muslim parents who already don't like sending their children to school." Especially girls.

- Some 'lost their minds' -

Surrounded by fellow pupils, Ali Abba pulls out his cellphone to show them a series of gruesome images. In one, about 20 bodies are heaped on top of each other, in another you see burned out cars.

"These are pictures of the Gamboru massacre," said Abba, who says he was in the town two days after the attack.

The raid on Gamboru took place as students were sitting their final exams.

"When the explosions started all the students abandoned their work. They jumped out of the windows to escape" and some were later found up to 15 kilometres away, said Nyioto.

"Some were crying, others completely lost their minds," the headmaster explained, adding he was concerned about the students' "sanity".

The students are not the only ones suffering.

Five teachers hastily left town before the end of the school year as the danger mounted, and the highschool has only 10 teachers left.

"The establishment risks being left empty. Everyone says they are going to leave," says the headmaster who has vowed to stay put.

Cameroonian soldiers which arrived in Fotokol a few days ago as part of an effort to beef up security in the region, are seen as the school's only hope.

Some 300 soldiers and paramilitary officers have been deployed in the town to provide security for residents and allow children to safely attend school.