Well historically people who were deaf/hard of hearing have been mislabeled as mentally delayed, autistic, emotionally challenged etc...now it is being identified much better but there are generations of pain and anger over this and culturally it still affects the deaf/hard of hearing community as a whole. So just given that broadly generalized history, there are many issues that can happen. Just intuitively it makes sense, right.... you miss things here and there and behaviors arise... if treated as if you are misbehaving due to a willful issue then resentment and frustration etc. could result. Not saying that is your case....just thinking of the links that can happen. A mild loss, in and of itself can be a problem and if this test was done on a "good" day (that is no infection/fluid this time) there still could be on again and off again greater loss which can train the mind to tune out......in addition if there is pressure/pain on and off or general ill feelings that can sometimes happen there is another layer of issues. Research on that for sure is around because I remember in the 80's having tests discussing it (do NOT ask me to go dig out my antiquated books, LOL... )
So much like a child who can't pick out important sounds due to auditory processing challenges a mild loss can result in behavior issues because a child may miss cues, may make mistakes, may appear to be ignoring and be corrected for those mistakes, and because he is likely to do well in some cases and no in others people may say it is "convenient" hearing and that he is choosing to ignore. Kids end up living to expectations or they can not want to admit that they really dont know or missed something (and often they dont even know.... they just are automatically compensating)
(do you mind sharing the frequencies and thresholds?? is the loss more in the high frequencies, middle, low?? do they feel it is a conductive issue (outer ear, middle ear--the bones and ear drum etc..) or a sensory neural loss (the inner ear/nerves going to the brain))
Hope they give him what he needs and the teachers can learn to adjust their presentation style to help.
I would absolutely push for an fm system and if they decide to do sound field (speakers that receive the main talker's voice and raises it by a predetermined decibel level over the ambient noise...his hearing loss would be factored in based on the type of system) then make sure it is available in all rooms he goes to. Q uses a personal one so the receiver is like a small hearing aid which he thinks is cool... I get it that is weird and some kids may complain. there are systems that can look more like music ear phones too... If this is a Special Education class that he is in mostly...the teacher may find it a huge help to have a sound field FM system in her class! Research is really good for use for adhd, processing, autism, any issue that can make attending to the more important sounds (like a teacher's voice or a movie or whatever) improved.
A big part of course will be making sure the teacher is not talking with their back to him and that for class discussions, they point to the person talking (if a fm system may need a class mic...some use one that they pass around and no one knows who it is for when the speakers are used....and some use a group mic.)... and as much as possible build up visual tools.... list directions so he can start to build compensatory skills.
Even if this is a small thing in the grand scheme... every little thing for our difficult child's (MHO here) can be huge compared to other kids with a mild loss.
I had a moderate loss in one ear for about three months many years ago ...as an adult. I swear the cosmos/God/something or someone wanted me to experience how much that can impact life. I about left a conference in tears because of the effort to listen to the speaker and then keep up with table conversation. This was not at my main job which was a school for the deaf , if it had been there I would not have been so left out...it was awful and I have tools to compensate! It can exhausting trying to catch information that you miss...then the exhaustion can cause behavior issues too.
Sounds like your gut says this could be an issue that really may be affecting him in more ways than just not hearing a little now and then.... you know him so I would trust your gut with that. (HIM?? I forget)
http://www.acoustics.org/press/133rd/2paaa2.html
https://www.msu.edu/~huffma23/
http://www.betterhearing.org/press/articles/pr_no_child.cfm Even mild hearing loss can cause serious problems for children. Yet, hearing problems remain one of the most commonly under-recognized and under-addressed issues in the classroom today.
Glad you found some clues... hope addressing it is helpful for difficult child.