First of all, let's talk about the problem of 7-year-old boys learning wind instruments. Learning wind instruments has many benefits for children, including improving musical skills, enhancing sense of rhythm, cultivating patience and concentration, and enhancing physical coordination. However, the 7-year-old children may not have strong breath because of their young age, which may become a problem when playing wind instruments. Wind instruments usually require some breathing control and skills, which may be a challenge for younger children.

As for the clarinet, it is a very interesting instrument, which needs some skills and practice to master. For 7-year-old children, clarinet may be a bit difficult to master, because its playing method and mouth shape require some skills and practice. If a child is interested in clarinet, he can try to get in touch with it in music class to see if he likes it, and at the same time see if his mouth shape and breath are suitable for playing this instrument.

To sum up, it is ok for a 7-year-old child to learn wind instruments, but whether it is suitable or not should be chosen according to the actual situation and interests of the child. If a child is interested and willing to devote time and energy to study and practice, it will be of great benefit to him. But if the child doesn't like it, or finds it unsuitable after trying it, there is no need to force it.