The reason that most children have low iron which is an iron deficiency is because of a poor diet.
Basically the child is not eating enough foods or the proper foods that contain the amount of iron that the child needs.
A child can take iron supplements as well to help raise the iron content in their body which is essential.
The child may also have anemia when they have a low iron content and that can make them tired as well.
Some signs of low iron or iron deficiencies in children or anyone else are pale skin, cold hands and feet, fatigue, slow growth and development, poor appetite, behavioral problems, abnormal rapid breathing and frequent infections.