So you are dealing with the 'top 25%' - so it's normal to get a week on place value.
You can ask for a subject acceleration or to compact the curriculum or to do Math online. You can ask for the top 2 or 3 to be given a special project to work on while the rest of the class repeats the topics. You can ask to homeschool Math and let him have a study hall.
Would any of those options suit your child? You can also try to arrange challenge in some other part of his life and let the Math Flap. It would be interesting if the teacher was willing to take a look at his pretest and see that the teacher thought about if this particular placement is the best fit.
Best Wishes,
Grinity
