You may need to get some evaluations done outside of school... but based on your descriptions, I'm going to "slightly" disagree with my good friends above... it might be something on the Autism Spectrum Disorders (ASD) spectrum, but it could be just as likely that it is a combination of other things - many of which often occur as part of the Autism Spectrum Disorders (ASD) spectrum and/or are comorbid with it.
evaluations:
1) Occupational Therapist (OT) - sensory and motor skills. Rarely will a school setting provide an in-depth Occupational Therapist (OT) evaluation. Fine to get the school version too - if THEY flag sensor or motor issues, it definitely has to be there! But... I'd still get a private Occupational Therapist (OT) evaluation.
2) Speech Language Pathologist (SLP) evaluation - he's a bit younger than they usually catch some of these problems at, but... he does SO much better one-on-one than in a class? That just screams "Auditory Processing Disorders (APD)" to me... auditory processing disorders, especially auditory figure ground. If you have this problem, it takes so much effort to filter out and pick up on the "words" being spoken, that there isn't enough brain-power left to actually "process" the message. Burn-out, and behavior problems, and "ADHD symptoms", are very common. Auditory Processing Disorders (APD) can be a stand-alone diagnosis, or be co-morbid with a range of other dxes, including ADHD. Where I live, they won't test for auditory figure ground until age 7... but it sounds like there are some screening tools out there that can at least "flag" the possibility... so he can get interventions and accommodations.
And then add in the others listed by other posters... testing for LDs, etc.