Very true. I am a teacher, and we receive training every year on the signs that a student may be in danger. Often they are things such as change in appearance, selling or giving away personal items, and verbalizing it is just one of many signs.
If I see a student disengaged or withdrawn in class, especially if this is unusual for them and they are not just introverted, I will make it a point to talk to them privately and just ask them how they are doing. This conversation will reveal a lot to me, but I am watching for signs before this conversation occurs.