HI Josefer,
The reason for a student withdrawal is many times a tough one to really determine. So I don't have a real clear answer to why many of the leave, except to say that they feel overwhelmed with life. Their outside of school demands drift into the classroom and the problems start to occur with their school work.
Experience has shown me that through developing rapport with the students I can get a feel of where they are at and if they are struggling. I also poll my students on a regular basis so I can get a feel for the climate within which they are working.
I work very hard at keeping the students motivated so they want to come. With this motivation I have even encouraged students to step out of school for a period of time and then step back in. This approach gives them an out, but they know the door is always open to them. I know it sounds strange but it does work in certain cases. The reason I am very selective with this approach is the easiest thing to do is quit and the hardest is to come back. It is like a diet or exercise program the first day is ok but after that it is like work so people quit and find starting again almost impossible.
Another thing I do is to study student profiles so I can look for indicators. By charting these indicators I can get a picture of potential school leavers vs the career completers. I am constantly looking for trends to help me with retention. All of these methods have been helpful.
Gary