My son has ADHD/Asperger's. My husband, who has multiple graduate degrees, took several long years to admit there was anything the matter, and had to be dragged through the diagnosis process. Why? Because he has ADHD and Asperger's himself, and feels happy and fulfilled, and doesn't want anybody fixing in his son what to him is normal. He is grudgingly coming to terms with the fact that he is not typical, and actually has some atypical challenges and strengths, which is a first step towards recognizing that his son needs help as well. In 20 years, I am fully expecting him to say that I was right all along and thank goodness I intervened early
So perhaps this child's parents have a similar outlook.
There is no magic cure or pill, apart from prescription stimulants for executive function (Ritalin and such), which this child will not receive before he is 18 since his parents won't have him evaluated.
What you can do:
1. Discuss this with his parents with the Nobel Prize - level diplomacy of an Israel-Palestinian peace talk, without mentioning meds, or ADHD or Asperger's! Frame it in terms of attention issues at school (or to cross the road), organizing himself (not forgetting to hand in homework), limiting self-stimulation, understanding social context and non-verbal cues better - all to get better grades, not get bullied or teased, have friends and be more successful. Point out that social skills groups are quite helpful for that, as well as organizational coaches. His own parents can teach him how to study efficiently at home. They can request extra time from the school is he is too slow, which would come in handy for the SATs and high school exams. The school can also give him preferential seating next to the teacher to avoid distractions, repeat directions to him, etc. Many schools will require a diagnosis first, hint hint.
2. I told you there was no pill. There is one - caffeine, the best-known legal stimulant in the world. Its activating effect on dopamine is proven. Dopamine is the neurotransmitter that is lacking in ADHD brains. A little caffeine goes a long way, because there is such a thing as adrenal fatigue when you've had too much. Find the minimal dose that works for him, and tell the teacher that his best work will be in the morning.
3. Help this child directly by giving him books is a great idea, if his parents don't see it as high treason. When he turns 18, you can also advise him to get himself evaluated for ADHD and/or Asperger's, and get medication and receive accommodations from his university's disability services.
Good luck. My nephew has ADHD and slight Asperger's tendencies. His parents (DH's brother and SIL) never had him evaluated, even though he receives extra time at school. He barely passed his end of high school exams, and is going to a trade school. Too bad for such a sensitive and artistic soul, but that's what happens when you stifle a child's potential.