Employment of substitutes — Retired teachers.

Persons who have retired as teachers under the provisions of subchapter I of Chapter 20 of this title; or subchapter II of Chapter 20 of this title; or subchapter III of Chapter 83 of Title 5, United States Code; may be employed as substitute teachers in the public schools of the District of Columbia when it is not practicable otherwise to secure qualified and competent persons. Any such persons granted temporary employment under authority of this section shall continue to receive their annuities during such employment and no deduction shall be made from the compensation of such persons for retirement benefits. The service rendered by such retired teachers employed as substitute teachers shall not be used to recompute their annuities.