Apologies are made for the lack of costumes - and weapons.
"Those aren't toys, you know," says Nasir Khudayer, their teacher, nodding at pictures of a past performance that used real AK-47s and rocket propelled grenades as props. "If we need them, these boys are ready to fight."
For today, imaginations will have to make do. Two boys stand in as US soldiers as another boy solemnly holds a green Mahdi Army flag. In English, one shouts out: "Excuse me please, what is that?" When his "American" companion says it's the standard of the Mahdi Army, they rush over shouting "No Mahdi, No" and rip and trample the flag.
A firefight then ensues, and the piece ends with one of the boys weeping over the boy playing the martyred Wael, who is then draped in an Iraqi flag and carried off on a plank to his funeral while the boys chant "Our blood and souls for you, Moqtada."
"The Mahdi Army is important to save Islam and to save Iraq,'' says Abid Ali Mussa Jabar, 12, fingering a combat knife. "We have to remember them."
Sheikh Saadi, the Mahdi commander, says that while the movement's stature has been mostly built up in relation to the Americans, its mission extends far beyond the day when US troops leave the country. "We're fighting a war to cleanse the world of evil, it starts here but will spread everywhere,'' he says. "It's going to last until the Mahdi returns to earth."
The Mahdi is a mythical figure revered in some Islamic traditions which closely mirrors some Christian beliefs about the end of the world. The Mahdi, the story goes, will one day return to Earth in the midst of violence and moral crises, bring about the full triumph of Islam, and usher in a long period of peace - to be followed by the end of the world.
Many of the group's leaders believe the time of the Mahdi is near. "Saddam's fall was a sign, the US occupation was a sign, our job is to prepare the way for the Mahdi's return,'' says Sheikh Uday al-Maliki, a Mahdi commander who calls himself a parapsychologist. "One way to think of the Mahdi Army is as a Mukhabarat for souls,'' he says, referring to Saddam Hussein's feared domestic intelligence service.