“My son will be 18 years old this July 2007 and he will not graduate till June 2008. My understanding is that I have to pay child support till he gradates June 2008.”
In California, that is absolutely the case. Support of a minor child continues until the child turns 18 and is graduated from high school or reaches the age of 19 in any case. There may be exceptions for college education or adult special needs children in some jurisdictions.