Dateline NBC to Kids -- Smile! Your Parents Set You Up in Our Cheating Investigation

Dateline NBC pulled a fast one in a hidden camera investigation last night -- but instead of targeting pedophiles, they took down middle schoolers cheating on a phys ed. test ... and the kids' parents were in on the sting.

Here's the premise: the kids were told they have to complete an obstacle course to audition for an "ultimate challenge" TV show. Unknown to the kids, Dateline is secretly recording the test ... and they've planted an actress who encourages the kids to cheat by inflating their scores. Also, their parents are sitting in a nearby room watching the whole thing go down.

The first time through the course the kids try to stop the actress from lying ... and insist on posting their real results. However, the second time, some of them give in and agree to fudge the numbers.

Natalie Morales then walks out -- playing the Chris Hansen role -- and tells the kids they've been set up to see if they cheat. The shocked looks on their faces are priceless ... especially when they hear their parents were in on it.