Final answer:
Mr. Baer should first contact the school system's attorney to seek guidance when he receives a subpoena, to ensure compliance with legal requirements and to protect the student's confidentiality.
Step-by-step explanation:
If Mr. Baer, the school counselor, receives a subpoena to disclose information regarding his work with a child whose parents are in a custody dispute, the first action he should take is C. Contact the school system's attorney to seek guidance. This is because legal matters involving disclosure of sensitive information must be handled in accordance with the law and school policies. Contacting the attorney will ensure that Mr. Baer complies with legal requirements and protects the student's confidentiality as much as possible. In such situations, the involvement of legal counsel is paramount to navigate the intricacies of privacy laws, parental rights, and court orders.