The folks at Outreach Inc. want you to mark your calendar for Sept. 13 and join other groups in planning a "Back to Church Sunday" to woo the "dechurched" and "unchurched."

As millions of Americans head back to school, organizers of a new faith-based outreach campaign hope millions more will come back to church, as well.

The "Back to Church Sunday" campaign from San Diego-based Outreach Inc. makes it easy for church members to invite their friends and family by creating a worship service specifically geared toward visitors.

The program kicks off with national "Back to Church Sunday" on Sept.13 aimed at reaching the "unchurched" and "dechurched" -- people who used to go to church, but don't any more.

The campaign is based on a simple idea. If you ask unchurched people to come with you to church, mostly likely they'll say yes.

LifeWay Research, an arm of the Southern Baptist Convention, found that 82 percent of un-churched people surveyed said that they'd be open to visit a church, if a friend or family member invited them.

Unfortunately, said Thom Rainer, president of LifeWay, few church members invite their friends and neighbors. "Only 2 percent of church members invite an unchurched person to church," he says. "Ninety-eight percent of churchgoers never extend an invitation in a given year."

While most Americans say they believe in God, and many tell pollsters they attend church regularly, only about 20 percent of Americans actually show up in church on Sunday, according to the "The American Church in Crisis," a recent study of church attendance.