First, take a deep breath and don't panic. Your son's the same son you've been living with and love. That hasn't changed (but you'll start making some AHA connections).
My DD9 has the same thing -- her hearing problem is weird in that it's in both ears, right at the 2000 level, speech tone. The ENT will check to make sure the ears are healthy, and redo the hearing tests. If they're consistent with the school's test (our school sent us to the audiologist first), then the ENT will tell you next steps.
Start your paperwork trail and stay organized with a good filing system. Keep all reports, and only give copies to the treatment team members.
This disability can and will affect his learning, and you should start doing some research about services the school is required by law to provide to him. I would talk to the teacher, and look up the process for requesting a service team review of your child's progress in class.
My DD's hearing loss is insignificant (and she has a very loud teacher this year), so we were denied the IEP (Individualized Education Plan) under section 504 this year. The paperwork's started, though, so that if it is degenerative or if she gets a softer-spoken teacher next year, we have everything ready to go for special services if necessary. You're your child's best (and often only) advocate, so get your ducks in a row as you prepare to ask the school for services to which he's entitled.
For us, the school's audiologist sees her every six months, and the ENT wants to see her every six months, so she's basically having a detailed hearing test quarterly.
Ask questions. Write them down before you go to the appointment, so that you don't forget them. Hang in there.