Yaroslav and Nazar, both 11 years old, are standing firm under the Ukrainian flag at a pretend checkpoint on the outskirts of their village in eastern Ukraine. 'We stand here and stop cars to check if the people are Russian,' says Nazar, conjuring a menacing look. Schools reopened in Ukraine in September. For students near the frontlines, classes are online. And when the final bell rings, it's back to their roadside posts. 'GLORY TO THE HEROES!' 'Glory to the heroes,' the driver, 39-year-old Oleksandr Yvanik, says, playing along. A few other popular 'passwords' are exchanged -- including an insult to Vladimir Putin. 'They understand that the enemy came to kill us,' he told AFP. 'We check their documents and car registration papers,' says Arten. 'We are here all day every weekend.' Carrying a wooden rifle, he waves to passing Ukrainian soldiers.