It is important for children to take high quality whole food multivitamins. it must say whole food, not natural on the label.
If the vitamin D in the mutivitamin is not sufficient a D3 supplement is necessary. Mercola makes a vitamin D3 spray that is great.
Omega 3's are also very important to boost brain power.
Probiotics are especially important, they improve the child's digestive system so they can absorb their vitamins.