American troops have been in Iraq longer than the average high school freshman has been alive. But for the most part, the deadliest U.S. military intervention since the Vietnam War remains a footnote in America’s social studies classrooms.

Fifteen years after the U.S.-led coalition invaded Iraq to topple Saddam Hussein, teachers and education leaders are still trying to find ways to teach students about an intervention that has yet to end.

The challenges teachers face are obvious: In a world where there is always too much to teach and standardized tests reign supreme, recent history tends to get left behind, even if this history is essential for understanding modern geopolitics.