As mentioned above, laptops are more easily damaged and much more difficult to repair. When you have to replace any component of a laptop computer, most often, you must have the exact replacement part for the laptop that has been made by the computer manufacturer for that specific model. With a desktop, you can go to your parts stock and almost any similar part will fit and work well.
With a desktop computer, opening the case is usually a simple operation and exposes all the components. With a laptop, opening the case can be a major exercise that requires several steps, and when you finally get it open, all the components are usually not exposed and then are difficult to repair or replace.
It seems that the laptop computer has become a status symbol for students, and even some schools. Students, and even some school administrators, usually don't understand the complications of having a computer that will have the characteristics discussed above. When their computer stops working however, they find themselves in a crisis with little money to pay someone to make the necessary repair and pressed for time to get their computer working.
We give computers to students who can not afford to buy a new computer. We are are very careful who we give a laptop computer to, when we have one available. If they are a serious older student, we have given both a laptop and a desktop computer to them so that they will have a backup computer when their laptop stops working and they need to complete a school assignment quickly.
I have included a link to this discussion on our web site to help students, who want to apply for a computer from us, to understand some of the issues with having a laptop computer.
I appreciate the others who are a part of this discussion.