Story highlights Tokyo Korean Middle and High School one of 10 schools in Japan with ties to North Korea

Portraits of N. Korea's founder Kim Il Sung and previous leader Kim Jong Il hang on walls

17-year-old Kyong Rae Ha: We just want to study Korean culture and language

Most of the students were born in Japan, which colonized united Korea until after WWII

On the surface, it resembles just about any other high school in Japan -- or any high school in most places around the world.

Students sit quietly studying math, science and English; some struggle to stay focused, looking at the clock and waiting for the bell to ring. When the school day ends, some move out to the sports fields for rugby or soccer practice, while others study music in emptying hallways.

What makes this school different is the pictures of two men scattered throughout the building -- portraits of North Korea's founder Kim Il Sung and previous leader Kim Jong Il.

The Tokyo Korean Middle and High School, which is currently home to 650 students, is one of 10 high schools in Japan with long standing ties to North Korea.

It's something the school's principal, Gil-ung Shin, is very open about.

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"Yes, North Korea has given us financial support over the years, sending us money and textbooks," he says.

The school also organizes annual trips to Pyongyang, where students are given highly orchestrated tours of the reclusive North Korean capital.

But the students we spoke with laughed at suggestions from some quarters that they are being trained as spies.

"People think we're being brain-washed. We're not. We just want to study Korean culture and language," 17-year-old Kyong Rae Ha says.

Sang Yong Lee, also 17, laughs at such notions, saying, "No, I'm not being trained to be a spy. This is just a place where I can show my pride as a Korean, living in Japan."

In fact, most of the students were born in Japan, as were many of their parents and grandparents. Korea was a Japanese colony until the end of the Second World War, and many Koreans were brought to Japan -- many against their will -- before the country was eventually divided between north and south.

But the mistrust runs deep, and many Japanese are wary of such schools.

Fresh on the minds of many in Japan is North Korea's admitted kidnapping of Japanese citizens from Japanese soil in the 1970s and 1980s.

Pyongyang says it considers the matter resolved, but Japan has long demanded more answers.

North Korea's strategic posture has also alarmed Japan. There's concern over an imminent nuclear test by North Korea -- which would be its third since 2006. And in December, Pyongyang launched a rocket that it said put the Shining Star-3 satellite into orbit.

But that is only a small part of the equation. Amid increasingly threatening rhetoric from North Korea towards its neighbors and the U.S., Japan's new Prime Minister Shinzo Abe is steadfastly refusing to consider requests for government funding for any pro-Pyongyang schools in Japan.

It's a high stakes battle for millions of dollars.

The students and their families argue they should get help with tuition from the central government, and the school should receive subsidies from local prefectures.

They argue that they are no different from the students at other international schools in Japan, which are afforded such luxuries.

"We pay the same taxes as everyone else," Kyong Rae Ha says. "It makes me angry as well as sad."

Shin acknowledges the abductions, and says the students learn about the crimes.

And when we ask about the ever-present portraits of North Korea's leaders -- portraits that also hang in his office -- and whether he's thought of taking them down, he says it's simply a way of saying thanks to those who've helped fund the school over the years.

But he adds, "We don't force the students to pledge their loyalty to anyone.

"I just feel bad that my students are caught in the middle of all of this."