The STPCD requires a teacher employed full time to be available for work on 195 days in any school year, on 190 days of which the teacher may be required to teach pupils and perform other duties as described in full in the STPCD and on five days of which the teacher may only be required to perform other duties.

These five days are known as teacher days or INSET days. No pupils are in school on these five INSET days.