Why do UAE schools prefer Native Speakers? Do they find non native speaker are not capable enough?

yes, without competition  and without giving you any chance to prove that you are expert , most American and British schools and colleges , not only in UAE but also in another Arab country and especially in Gulf country, demanded to hire only native speaker. after 1990, the Americans succeeded to find an education market in the Gulf and to dominate this field, but the goal is not the education itself, but the way to spread their culture and to gain Arabic followers. 25 years later, most of the gulf people spoke English, culture changed and now you can see American company dominated the market. In other side how much these Arabic people benefits from american education and curriculum? Till now, the council of gulf country continue to hire residence from outside to run, manage and take care of their companies, school, hospitals universities.... for which reason a 3 years child need a native speaker in Nursery?

Not at all, Shamini.  It's all about the accent I think and the fact that the native speaker will also use lingo or phrases that are culture specific.  I think that any teacher that is committed to her students and to the teaching aspect of this position can more than qualify.  It is a current bias that is trending so you have to show how the right skills are just as admirable as the accent.