Child 17 years old, immigrated to Washington, USA to study. Guardian can't go. Can he entrust it?

Whether you need to go through the custody procedures for your child depends on your personal decision. It has nothing to do with school. If there is no formal guardianship procedure. The school regards his aunt as a contact.

His aunt can naturally be the guardian of the child. Have the signature of the main parents or need your signature. Other aunts just sign their names.

Immigrate to study? Is it a public school or a private school?

Supplement to the question:

Ask if your school must go through the formalities. Public schools? Most private schools do not require it.

I am in Delaware. If necessary, I can send you a sample of the guardian agreement.