December 6 (St. Nicholas Day) is Finnish Independence Day. The Grand Duchy of Finland declared independence from the Russian Empire on December 6, 1917. The Provisional Government in Petrograd had been overthrown in October, and the Finns weren't sticking around for Comrade Lenin's "great proletarian revolution."
Finland's national anthem is Maamme (Our Land). I've had a couple renditions bookmarked on YouTube, but found this one last week. I thought you'd love to have the schoolchildren sing.