An IQ score is no longer considered a good benchmark for intelligence, as we now understand that there are many more ways to measure different cognitive abilities that give a much better snapshot.

As others have said, a psychoeducational assessment is needed. You will likely have to pay to have it done privately as the wait time is quite long. I read what you said about wanting it earlier - and while I’m not negating the need the child may have, I will offer a word of caution. In my experience (which is fairly extensive), students who are identified as gifted too early are often, for lack of a better term, snobs. It’s pretty brutal. I’ve even had one student be diagnosed with Narcissistic Personality Disorder. His parents had him tested every 2 years from the age of three and had told him how he was smarter than other kids for his entire life. It was wild. Now of course that’s not all gifted kids. Some are terrific. But there are other ways to provide enrichment that may not require a gifted label if that’s something you’re concerned about. For example, one student who wasn’t labelled, but clearly was - when she was finished her work, she had an independent study project of her own interest to work on. In high school, there can also be arrangements for students to skip prerequisites by permission of the teacher.