It depends on which church. 

Research shows that "mainline" (read: liberal) churches are losing their youth (2.2% decline from 1991-2012). But evangelical churches actually gained over the same period (0.6% increase). 

These numbers are from a Pew Forum study, reported by Glenn Stanton of Focus on the Family in First Things.  

Another factor that skews the numbers is that many who are counted as "leaving" church are simply switching to another church. Stanton writes: 

Young adults who are merely moving from one faith tradition to another, such as from Lutheran to Presbyterian, or Anglican to Catholic, are simply counted among the "leaving." Professor Byron Johnson from Baylor’s Institute for Studies on Religion confirms this, "Switching is not an indication that Americans have abandoned or lost their faith, as many in the media and, unfortunately, a number of Christians would have us believe." Changing lanes from one Christian tradition to another cannot honestly be categorized as "leaving" their faith.

Finally, among those who do lose their faith, most never had much to begin with. Stanton explains: 

When considering those who do leave the faith in young adulthood as a category, only 11 percent said they had a strong, meaningful faith as a child. A whopping 89 percent said they did not. 

What the numbers really show, then, is that liberal churches are shrinking, while evangelical churches are growing. Of course, we've known that since 1972 when Dean Kelley wrote Why Conservative Churches Are Growing. Kelley, an executive with the liberal National Council of Churches, realized you could not just lump all churches together. But the news media, Christian and secular, have been doing just that.

The lesson is that parents and churches who teach and exemplify Biblical convictions in credible ways are very likely to succeed in passing along those convictions to their children. As Stanton writes, what these numbers suggest is "that young people respond positively to a call to substantive discipleship and scriptural study. They are looking for something that calls them to be radically different."

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