Do I have to go to court to adjust child support with multiple kids when one graduates high school?

Sometimes support is ended for the child no longer requiring child support by the amount of support designated for that child just removed from the support payment.

However, you need to check with your local court to see if they require you to file a motion to terminate child support for that child. If so, then you will need to file the appropriate motion and obtain a new order.

If you have a wage assignment order you will also need to modify that as well.