To provide efficient and effective use of IEP Team meetings, the parent and the LEA may agree to excuse any member of the IEP Team from the IEP Team meeting if their area of curriculum or related services is not being addressed.

The parent and the LEA may also agree to excuse any member of the IEP Team from the IEP Team meeting if their area of curriculum or related services is being addressed, but the Team member will be required to submit their input in writing to the parent and the LEA prior to the IEP Team meeting. 

The parent must provide written consent to the excusal of any IEP Team member.  Source:  IDEA Guide to Frequently  Asked Questions.