Why did the gifted school suggest starting him with the fourth grade curriculum? Honestly, that seems more odd to me than the French school wanting to start him with first grade math in French.
I recently worked through several of our state EOG math exams with my kids. Yes, they learned it really fast, but they still needed exposure to some of the stuff. Obviously your son has a facility for math to understand division intuitively and to do the doubling required to figure out 2^8 (did he just do the calculation or does he understand raising numbers to a power?). In my (kinda backwards) state fourth graders know how to work with fractions, reduce fractions, add fractions, understand decimals, convert fractions to decimals and vice versa, derive diameter from radius and vice versa, calculate the area and perimeter of a rectangle and two joined rectangles, find the missing measurement when given area and length of one side, find the measurement of the third angle of a triangle when given the other two, do basic algebra, understad how to convert from cups to gallons, quarts, etc., and even some probability. Well, actually most of the kids can't because I figured out that "meeting state stnadards" meant getting about 50%, but it's part of the curriculum.
I would be interested to hear how the gifted school determined what would be appropriate placement for you son. Maybe it is obvious that he requires that level of instruction, but going only on what your've written it sounds a little extreme to me.
