Here's a very interesting paper from Germany showing how attentional and executive control networks change with development. The study used a visual attention task and compared healthy 8-12 year olds and 20-34 year olds. These sorts of studies are important to understand the normal development (that is, not ADD or ADHD) of attention in children. The different patterns of attentional activation were seen even when test subjects were controlled for performance. So kids are using different areas of the brain for paying attention, even when the attentional scores are the same.
Also check out this neat figure looking at test trials using an incongruent or distractor object. Adults were better at activating their inferior frontal gyrus - so it did not suggest that distractibility was simply a lack of focus. Rather the more distractible group of children were just not as efficient at "letting go" of their focus once it had landed on the distractor (novel stimulus). 'nother interesting tidbit, the inferior frontal gyrus was mentioned in an earlier post of ours (link below)...for its role in determining "resiliency".
Developmental Changes in Attention
Eide Neurolearning Blog: Mental Toughness, Resiliency, and Endurance