Education: teachers; certain school employees; allow to serve as short-term substitutes. Amends sec. 1233 of 1976 PA 451 (MCL 380.1233 ).  TIE BAR WITH: SB 0263'21 , SB 0268'21 , SB 0264'21 , SB 0057'21 , SB 0266'21 , SB 0260'21 , SB 0056'21 , SB 0262'21 , SB 0261'21 , SB 0265'21