Its such a shame kids today can't take a few seconds to search for information online. And can't be bothered to see if some other kids have already asked this exact same question. This is one of the most frequently asked (and answered) question in Astronomy.
http://www.kidsgeo.com/geography-for-kids/0045-why-is-the-sky-blue.php
http://www.whyistheskyblue.co/for-kids.php
http://spaceplace.nasa.gov/blue-sky/en/
Its a sad statement on the education system that doesn't teach science and doesn't teach kids how to learn.