That's when the Atlanta educator saw the US$365,000 (S$524,000) check for the innovative private school he opened in one of the city's poorest neighbourhoods in 2007. It was, quite literally, an answer to a prayer.

'We teach school all day and fundraise at night,' said Mr Clark, who finds private donors to pay most of the US$14,000 annual tuition for each student. 'To have an unsolicited gift come like that is incredible.'

Mr Clark surprised his students with the news of the donation on Wednesday morning in a gathering at the south Atlanta school. The children, parents and teachers erupted in deafening cheers when he showed off the check.

Several cried at the news.

'Everything they learn is enhanced because of the teachers' dedication and creativity,' said a tearful Gloria Nesmith, whose son, Cameron, is a fifth-grader at the academy. 'And Oprah noticed. I'm just overwhelmed.'

The donation, which likely will go to scholarships for students, would pay for 26 children to attend the school for one year.

In her letter to Mr Clark, Winfrey calls him a role model and applauds the 'profound difference you're making with your passion for teaching'.

Representatives for Winfrey did not immediately return calls for comment.

The check was issued by the Oprah Winfrey Foundation, which gave US$4 million to educational programmes in 2008, said foundation executive director Caren Yanis.

The check was issued by the Oprah Winfrey Foundation, which gave US$3.5 million to educational programmes in 2006, according to the latest data available online.

Mr Clark and his students became overnight stars during the presidential election when a video of the students performing a political rap they wrote grabbed the public's attention on YouTube.

The children ended up performing the rap, called Vote However U Like, on national TV networks including CNN and BET.

Teachers at the school frequently use rapping, dancing and drumming to help students learn.

Mr Clark, who taught in one of New York City's toughest schools and wrote the best-selling teaching book The Essential 55, opened the school last year with proceeds from his book and private donations.

Nearly all of its 80 students are from middle- and low-income households. Parents pay a small part of the tuition and the rest is paid by donors.

Mr Clark has appeared on The Oprah Winfrey Show twice - once when he was named Disney American Teacher of the Year in 2000 and again when his book made the New York Times best-seller list. -- AP