Tex. Labor Code § 408.0446

(a) For determining the amount of temporary income benefits of a school district employee under Chapter 504, the average weekly wage is computed on the basis of wages earned in a week rather than on the basis of wages paid in a week. The wages earned in any given week are equal to the amount that would be deducted from an employee's salary if the employee were absent from work for one week and the employee did not have personal leave available to compensate the employee for lost wages for that week.

(b) An insurance carrier may adjust a school district employee's average weekly wage as often as necessary to reflect the wages the employee reasonably could expect to earn during the period for which temporary income benefits are paid. In adjusting a school district employee's average weekly wage under this subsection, the insurance carrier may consider any evidence of the employee's reasonable expectation of earnings.

(c) For determining the amount of impairment income benefits, supplemental income benefits, lifetime income benefits, or death benefits of a school district employee under Chapter 504, the average weekly wage of the employee is computed by dividing the total amount of wages earned by the employee during the 12 months immediately preceding the date of the injury by 50.

(d) If the commissioner determines that computing the average weekly wage of a school district employee as provided by this section is impractical because the employee did not earn wages during the 12 months immediately preceding the date of the injury, the commissioner shall compute the average weekly wage in a manner that is fair and just to both parties.

(e) The commissioner shall adopt rules as necessary to implement this section.