Is drinking milk healthy for humans? Why or why not?

Drinking milk is good for some people. On the other hand, drinking milk does not give a great effect to those who have allergies to milk. In my case, drinking milk has more disadvantages than advantages. The first reason is that drinking milk can prevent concentration exams. When I was a high school freshman student, I drank milk before the important exam. As soon as the exam started, I experienced stomach pain because of the milk. From my close friends\' perspective, they also avoid drinking milk before important events such as exams and presentations etc. People with lactose intolerance cannot fully digest the sugar in milk and this symptom can worsen when people feel nervous. This is the reason why I think drinking milk is not good for my health, however, drinking milk is great for people who do not have any allergies to milk and lactose intolerance.