Socks especially designed for motocross are an excellent compliment to any motocross boot. These socks are typically very think and will help your foot fit into boots that may be a little larger than desired. Most importantly, MX socks will reduce your chance of getting blisters. As you can imagine, blisters have the potential to end your day on the dirt and are certainly not desirable effect of motocross boots.
References:
http://www.newenoughmx.com/faq_kids_sizing.htm
http://www.newenoughmx.com/faq_kids_sizing.htm