Perhaps your idea of a small child at the flight attendant's idea of a small child are different.
However, the Southwest website specifically states: "A passenger seated in an exit seat must NOT: • Have a condition or responsibilities, such as caring for small children or pets, that might prevent them from performing the applicable functions." Some might consider an 11-year-old to be a small child. Additionally, I am an avid reader of the FlyerTalk forum and I have seen this topic come up regarding the same situation at multiple other airlines - One parent is in the exit row, the other parent is in another row with the child. The parent in the exit row was moved out of that row. In one of the FlyerTalk posts, a passenger said that every time he scans his exit row boarding pass at Alaska Airlines, the gate agents specifically ask if he is traveling with a child under the age of 15. So it does appear to be a policy at other airlines.
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