I'm a big fan of MAP testing, simply because it's a great way to show that your kid is progressing and learning something. If my kid's numbers are going up, I am happy. If they are not, I will investigate what's going on at school.
As for whether I think knowing a child's reading level is important, I'd lean toward yes if you're talking GT kids. In my experience, most classrooms are filled with grade level books. Some school libraries restrict what kids can read. So if you would like your child to be appropriately challenged, you will need to do the work as a parent and advocate for more at school or make sure that your kiddo gets appropriate materials at home. I would think a good number of GT kids will start to think that school is not a place for learning if they are not given progressively more challenging materials. Just my not so humble opinion.
