What can I do to get a lower child support payment?

My ex wife and I have had an informal agreement that I would pay $300 a month for child support and this way we left it out of the courts hand. Now she has used an online calculator that shows I should be paying 600 a month because she was laid off and has filed a formal child support order with the local court. My question is: What can I do about this as with my rent and other basic bills I could not afford to pay this $600 a month. Part of my question is this also. I was recently accepted into law school in the San Francisco Area. One of my ex wife's friends is an attorney and she informed me that the court would not allow me to attend school because the ABA imposes an amount of hours you can work per week and this would prevent me from being able to pay whatever amount I am ordered. Can the court prevent me from attending law school? Or would my child support be adjusted to the fact I would have basically no income outside of student loans?