Determining the "smartest" 12-year-old definitively is impossible, as intelligence is multifaceted and can't be perfectly captured by a single test. However, based on available information regarding IQ scores, we can identify individuals who have achieved exceptionally high results.
According to a news report from January 2024, Rory Bidwell, a 12-year-old from Great Torrington, Devon, scored the highest possible score for children (162) on the Cattell III B IQ test. This accomplishment places him in the ranks of Mensa. The article mentions that his score exceeds the estimated IQ of Albert Einstein (believed to be around 160).
Therefore, based on documented IQ test results, Rory Bidwell is a candidate for a particularly intelligent 12-year-old. However, other 12-year-olds may exist who have not taken such tests or whose scores have not been publicized.