Training plans and exercise selection are sometimes "monkey see monkey do" and other times extremely different for no other reason than for the sake of being different. "Monkey see monkey do", in my opinion, isn't totally wrong, since many great coaches pass down training theory and philosophies, I just feel you should know the "why" behind it before you implement it. There is really no need to do either of these things as long as you have confidence in your ability to develop a sound training program.
Here are a couple of things that should hold true when designing a training program and individual sessions.
Exercise order DOES MATTER. You can decide to omit any of these four things during a session, but it is ill-advised to attempt to change the order.
A common theme in the weight room is the more exercises you do in the allotted time, the more effective the workout. That has the potential to be true, but rarely is. In the weight room, priority should be given to the multi-joint, compound movements like Olympic lifts, squats and squat derivatives, presses, pulls, etc. Determine what type of training response you are trying to elicit and then select the appropriate exercises. Depending where you are in the season and what type of athletes you are working with, it may look slightly different, but this is how simple a weight room session has the potential to look.
1. Olympic Lift/Plyometric/Weighted Jump
2a. Squat/Squat derivative
2b. Upper Body Push or Pull
3. Abdominal/Assistance Lift
As you can see, this is nothing fancy. Using the correct volumes and intensities will get the job done. And done well.
Don't over-complicate things. Especially when you're dealing with athletes that don't have enough experience to benefit from a detailed training plan.