My kids would never climb out of a PNP because they understand, from day one that they are not allowed to stand up in their PNP. If you know you are not allowed to stand up in your PNP then you would never even think to climb out of it.

I teach the kids that PNP time is SLEEPING time and if you are standing then you obviously are NOT sleeping.

The first week I have a kid in care I literally will go in a thousand times, if needed, and lay the kid back down every time they stand up. They catch on pretty fast that they are NOT to stand up in the PNP.