I try never to leave someone behind. Lots of ways of accomplishing this. The make up of the ski area has a lot to do with how it's done & each can still ski variety of terrain & levels. Above treeline open or bowl areas are certainly much easier to leave no one behind.
Since I'm growing a skier, we cover lots of what ifs, terrain,& situational stuff. Besides falls, avalanches, treewells, someone could get hit by another skier/rider & be down & hurt. If you can't see 'em, you won't know. Does the other involved person even stop ? Or are they capable of helping ? The tree skiing in fresh snow absolutely requires following the rules of watching 1 skier go down & the 1st skier watching the next skier come down. Tree wells are a high incident of death when they happen. If your partner is doing their job right, you can live. I always recall the incident Eric & Rob DesLauriers describe in the their book Ski the WholeMountain, where Dean Decas lands in a treewell. Had those 2 skiers not been following the safety rules, Dean may not be alive for them to joke & tell stories about. So, we keep to the rule of no man left behind, and even then, sometimes someone gets split up. Plan B's need to exist.
Which brings up another subject for a thread. If you are playing line backer on the slopes behind your kid, if they lose you, (like you went down or were taken out) do they know what to do or where to go for help ? Do they know where to go for Mt. Safety or Ski patrol ? They were ahead & not sure where you got behind. Do they know where the Ski patrol office is ? What do they do if they find themselves alone without you ?
And the final question : If you are not hanging together , who's taking the photos of you or you of them for posterity or posting ?