California Code, Education Code - EDC § 44855

If the teacher from the district within the state who serves as an exchange teacher without the state and the governing board regularly employing him so agree, the district may pay his regular salary, making all deductions provided by law for retirement purposes, during the period of the exchange teaching.  In such case the district shall not pay the salary of the exchange teacher from without the state, serving the district in exchange for its regular teacher.

In the event a teacher from a district within this state serving as an exchange teacher without the state and to whom the governing board of such district is paying the regular salary of such teacher as herein provided, is compelled to absent herself from her duties because of injury, illness or quarantine, the governing board of the district within this state may pay the substitute employed to take the place of such teacher and shall deduct the amount so paid the substitute from the compensation of the teacher.