IQ tests are really expensive. School districts won't test over and over unless there is an underlying concern. Each time a person is tested, the diagnostician or psychologist has to use a different test from a different company. Private testing here has a minimum 6 month waitlist and costs between $1500-$2300 depending on the age of the person. The test (consisting of many sub-tests) is not given in a room with others testing at the same time. Testing happens 1:1 and takes several hours. Just to give a perspective, someone with an IQ over 130 is in the top 2% (98th percentile). An IQ of 138 is in the 99.5 percentile meaning only .5 people in the world are more intelligent. An IQ of 145 is in the 99.86 percentile. Online IQ tests are not worth the time it takes to answer the easy questions. Everyone who takes these has an IQ between 125 and 160 or higher.
I've seen IQ results be quite different on the same child. One of my own children tested above 130, but because of what I know about the tests, I question the validity of the results at times.