I have two boys (10 and 5) and their father and I have split custody. I have Sun, Mon, Tues and he has Wed, Thrus and Fri. We alternate Sat. I also have my older son every day after school to do homework. Being a teacher, I have a great deal of vacation time and like to spend it with my children. However, their dad insists that his time is his time and even if I am not working, the kids go to his mother's house. Anybody know if I can petition the court to change custody arrangements for the summer?

You can petition the court for a modification. Whether it will be granted is another question. I would suggest first trying to work out an equitable agreement with the father to present to the court.