Maybe you should get an audiology exam, not just the crude screening for hearing done at the pediatrician's. We found out that my then kindergartener was deaf in one ear by asking for an audiology exam, although the pediatrician said his hearing screen with them was normal 3 years in a row.
Speech delay and hearing loss frequently go together. Kids who are deaf in one ear are 10x more likely to fail a grade and have lower verbal/oral scores.