I recently randomly selected for pre-check at LAX-- I was flying with my two children, ages 14 and 11. The 14yo also had her boarding pass marked as pre-check, but the 11yo did not so we went through the regular line (because I didn't know that 12 and under could come with me in pre-check). Because 14yo and I had pre-check marked, though, we did not have to remove our shoes. We did have to separate our laptops for the xrays. Because 11yo was 11, she didn't have to remove her shoes, either. We all went through the metal-detector and not the full-body scanner. So in the regular line, it ended up as a kind of hybrid-regular/pre-check thing, and that's basically what the TSA agents said (but they did NOT mention the part where my 11yo could have gone with us in the pre-check line, which was substantially shorter- I only discovered that when I looked up pre-check after we had landed).