The pick and roll/pop is essential offensive play in basketball. It gives you advantage in a way that a faster players attack slower opponent, or your higher guy is guarded buy shorter defender. 

If you want to build solid defense for your squad, you should teach them how to defend screens and what are the key features in being successful at it.

Lets analyze the options that you have.

First, the important thing is knowing what is the level of the screen. It is a line that is formed by the screener and a ball defender.

Knowing this, and depending on the ball handler quality in therms of shooting/driving/passing, there are three options that you can choose.If you have semi good shooter, the player that is defending the screener can just make a horizontal movement, in the line with the level of the screen, and give the ball handler a notice that he is there. 

The moment your ball guard recovers from the screen, the big guy needs to reconnect with the roller. 

If you know that the ball handler is a good shooter, you need to chase away him towards the center. This way of defending the screen we will call HARD HEDGE.

The goal is not to make him dribble to the position from where he can take easy jumper. 

And in the third option, your player that is switching on screen will stay beneath the screen line.

In this case, you know their guard is not a good shooter, and by this play you will close the driving lane.