This corresponds to $FD6C in the ZX Spectrum version.

Used by MR WACKER in lesson $FE; by MR ROCKITT in lessons $E0, $E1, $F7, $F9 and $FE; by MR WITHIT in lessons $F7, $F8, $FA, $FB, $FE and $FF; and by MR CREAK in lessons $E0, $E1, $E2, $E3, $F1, $F6, $F7, $F8, $F9, $FA, $FB, $FE and $FF.