Firstly- the idea behind staying in the room is so that the instructor can keep an eye on you. The last thing we want is for you to exit the room, faint and hit your head. The chances of that are low, but they are non-zero.

Secondly- child pose is actually NOT recommended in the standing series. It is better to remain standing, or kneeling (or sitting cross legged). Entering child pose (or laying down) will make it much harder to re-engage with the class. Instead, sit. If you need to skip a posture, skip a posture. if you need to skip 10 postures, skip 10 postures.

Generally speaking -- for regular students -- follow the strategy of "do less better". When you walk into the room, you have control of yourself. Try to practice in a way where you don't lose that. Perhaps that might mean practicing one set of each posture. perhaps that might mean doing way less of Standing Head to Knee and Standing Bow. The practice is not supposed to be one where you hanging on by your fingernails for every second of the class. Not only is this not enjoyable, nor is is healthy, it is also not sustainable.

When it comes to new students, the idea is to practice in a way that allows you to come back again. One of my first teachers said something to the effect of "nothing worthwhile was ever learned in 10 easy steps". This is another way of saying that judging hot yoga after 2-4 classes is insufficient. Instead, do what you need to do to come back. Get more evidence, learn about the practice, and learn about yourself.