My sons vision at age 13 was 20/20 at age 14 it was -.25 and -.50. At age 15 it was -1.25 and -1.50 now at 17 it's -1.75 and -2.00 is this normal?

Myopia progression. Your child's eye is growing as he is growing which creates a degree of myopia. The vision 20/20 is different than the degree of lens power required to normalize the vision. Your son is progressing in a fairly typical sequence and he is likely to get more myopic until the mid to late 20s. This is a typical progression and not worrisome and his overall power need is not great.