At this age, it is really about balance of complex carbohydrates, lean proteins and healthy fats.
It is about fueling optimally and not dieting.
It is about abundance not restriction.
It is about life style and creating a new one over time.
It is believing that nutrition really has a value and a purpose and not just something to eat.
It is about realizing food is ONLY fuel for the body to be vibrant and strong vs eating because it is what I want or prefer.
At least 2-4 servings of fruit a day
At least 3-5 servings of non starchy veggies a day.
20-40g of fiber a day.
30g of added sugar or less a day NOT including sports drinks and chocolate milk around activity. Fruits and regular milk are NOT an added sugar.
Keeping saturated fats to less than 10% of total fats a day.
Eating 5-6x a day, every 2-4 hours based on their schedule.
Eating whole foods whenever possible.
Hydrate at least 1/2 their weight in fluid ounces a day.
No less than 8 hours of sleep a night.
You can track their nutrients on a free app called Cronometer to see where they are at.
Set a goal a week or 2-3 goals a month to start.
They should never eat less than 2000 units of fuel a day. If you think they do, it is time to seek out professional assistance. Many need 2500-5000 units of fuel a day on average. Also consuming too little will slow down growth and development.

In my academy you can find assistance in the gain lean weight , get leaner program or in fueling for performance daily menus.