The only IQ test I remember taking was in 6th grade. I scored 168 at that time.
One thing to remember about IQs is that they measure not what you know, but how quickly you can adapt, learn and retain what you learned. When you are young (earlier than, say 18 years old), your IQ is significantly higher than it is later on in life. A toddler's IQ is approaching 200 compared to the average intelligence of an adult. When you consider what they have to learn in an extremely short period of time (i.e. how to walk, talk, understand their birth language, how to push their parents buttons...) it is not such a stretch to realize just how intelligent they are.