Thank you for the input.
Failure to gain weight can be due to several factors.
This can be inadequate intake, inter current or recurrent illness.
Chronic infection, metabolic disorder, celiac disease, cystic fibrosis, endocrine abnormalities etc. are some possibilities.
Sometimes, genetic influence can be there.
Common illnesses to impede weight gain are infection, worm infestation.
If doctor thinks necessary hormonal studies, ultrasound examination, X rays,stool & urine tests can be taken.
You can discuss the above issues with his pediatrician.
You can take a few measures to increase his food & calorie intake.
Please try to make him avoid using i pad during taking food.
This may prevent his taking food in school.
Foods will not increase appetite but you can give him calorie, vitamin rich foods.
Milk will be good & can be given as snacks.
Please try to give him more food during breakfast & dinner as he is trying to skip lunch.
Give proteins like meat, egg along with bread, vegetables, fruits.
I hope this information will be helpful.
If you have any query, please feel free to ask.
If you are happy with my answer please click on the Excellent/Good rating.
Wish his healthy life.