Will child support automatically stop if my daughter is 18 and graduates in 2 weeks?

Here is the law in Iowa: Parents have a legal obligation to support their minor children. This obligation shall continue for a child who is between the ages of eighteen and nineteen years who is engaged full-time in completing high school graduation or equivalency requirements in a manner which is reasonably expected to result in completion of requirements prior to the person reaching nineteen years of age; and may include support for a child of any age who is dependent on the parties because of physical or mental disability.  Now, your agreement is also what is binding here.  Your ex may stop paying and then go to court has to ask for an order terminating the support.  So be prepared for it.  Good luck.