My thoughts about IQ testing...

Recently someone asked in an online forum whether she should have her preschool child's IQ measured.
For one thing, IQ tests do not measure everything. There was an article I read several years ago (and remember at one time kids and their parents were not shown IQ test results) about someone who won a Nobel prize in science who went back to his old high school and got a copy of his files for some reason, and learned that his IQ, as tested by the school system was NOT in the gifted range. Obviously, his IQ test did not meaure him properly.

Also, IQ isn't everything. There are a lot of good attributes that are not measured by IQ. When I taught 2nd grade, a parent asked that her son's IQ be tested, and it came out around 100. Her response was to be very upset that he was only "very average". I replied that he was not average, he was a very well-behaved, kind child who was very considerate of others and well-liked by his peers and his teachers, that he was doing very well in his schoolwork, and that she should not focus on that number. There are many people with lower IQs who, by virtue of diligence, people skills, and sheer hard work have been more successful than those who have a higher number on a paper in a file somewhere.
Another issue is that IQ can change, depending on whether a child has an enriched or a deprived environment. I once knew of a child who was adopted at around age 6, after having a very chaotic earlier life of foster homes and adoptive homes that did not work out. At that time, his IQ tested at around 80, which is not indicative of future academic success. He was adopted by someone who gave him a very enriched environment and a lot of help with schoolwork. He eventually graduated from college and thus far has had a very successful career.
If you are concerned about whether your preschooler has a high IQ, your focus should be on giving him the most enriched environment possible, as long as it is done in a fun way, not by force feeding them flash cards or phonics whatever. Reading to them, visiting interesting places, a lot of conversation with older people, toys that require the child to do things (such as Lego, Duplo, and other building toys) rather than toys that the child just watches, are valuable. Arts and crafts which are creative--drawing and painting, rather than coloring in coloring books. (Now, coloring books are not fatal, children enjoy them and coloring within the lines helps hand/eye coordination but they should be a small part of a balanced diet of activities) Helping adults in any way that they can help safely is also valuable (see my earlier cookbook recommendation).

In short, do not be concerned with your child's IQ unless your pediatrician or a teacher has expressed concern about developmental delays. And in that case, they will help you locate testing.