I give the question writer a failing grade on ability to ask a question.
If the question is instead, "The most common issue requiring formal special education assistance seen in school age children is.." Then this is the key to the answer:
â€œLearning disorder: A disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written that may manifest itself in the imperfect ability to listen, speak, read, write, spell or do mathematical equations.â€
Now if the question is just" the most common problem seen in school going children is ..." the answer is behavioral: paying attention, focusing, and maintaining self discipline. Often those are associated wiht a, b, c, and reading issues.
I have no idea what reading retardation means.