Yes. If your son is deaf, he has unique needs. The school is required to provide the services he needs.
Related services are the developmental, corrective, and supportive services your child needs to meet the measurable goals in his IEP and receive a free, appropriate public education (FAPE).
Interpreting services are related services.
The federal special education regulations include "special interpreting services for children who are deaf-blind" and an interpreting service.
Your child's IEP should include the frequency, duration, location, and projected dates for each related service, (i.e., when an interpreter will be provided).
Related services personnel should be included on your child's IEP team when a particular service will be discussed. The interpreter has special knowledge and expertise and can provide recommendations about what service is needed and how it can be provided. Either the parent of the school may invite people who have special knowledge and expertise to IEP meetings.