Hello, i can understand you must be worried especially considering he lives away from you and its a matter of academics. But help is always available. I suggest the following steps: speak to his teachers and get their feedback and assistance. Speak to his school counsellor if his boarding school has one. Finally armed with this information, you will be sufficiently prepared to approach a counsellor and get him tested/evaluated. All the best! :)

Take your child to psychologist. Do some assessment test for him. His problem needs psychological evaluation.

Respected Sir, I can understand your concerns regarding your son's academic performance but before giving any suggestions to "improve his learning power and ability", I would advise you to please check your son's IQ using standardized instruments by consulting a qualified clinical psychologist. If his IQ turns out to be borderline or even below that, you should consult a psychiatrist with those results who can advise you further regarding your son's abilities. On the other hand, even if his IQ turns out to be average or above average, even then a psychiatrist could help rule out other causes for the poor scholastic performance