M y son has codsey of his son his job is moving and he has to go .my son lives with his father and i.what I;m asking can she take the child if he lets the child go to school here. And spend the summer with him.

Let me see, this is very hard to read, periods at the end of sentences, and too many "son" named

But let me see you son has custody of your grandson

Your son is moving and he is??
a. now living with his father ( your ex I assume)
b. will be moving in with his father?

OK, who is "she" the child's mother?

The custody agreement should list specific visitation dates and custody dates. So what ever the judge ordered is what she gets to do.