The minimum scores for ACT are 18 for Reading Section, 17 for English Section, and 19 for Math Section. The SAT is usually taken in the early fall (October or November) of the senior year. A number of juniors take the test in the late spring (May or June) and take it again in the senior year.
An IQ score of 115 means performance one standard deviation above the median, a score of 85 performance one standard deviation below the median, and so on. Lewis Terman and other early developers of IQ tests noticed that most child IQ scores come out to approximately the same number by either procedure.
Your score will reflect where you lie compared to others in your age group. IQ tests are standardized to a median score of 100 and a deviation of 15. This means the most common score is 100 and 2/3rds of test takers score between 85 and 115. If your score is above 130 you're in the top 2.1% percentile. IQ tests measure your score relative to others so accuracy depends upon the quality of data being used to calculate scores.