5.5 hours a day?

[Lampshadelegs]

My pay slips say I work 5.5 hours a day but I (like all teachers) really work closer to 10.
If I did leave after 5.5 hours would this be fine because my contract is for 27.5 hours a week?

Teachers are required to work as many additional hours as necessary to effectively discharge their duties. However you only need to be on the school site for directed time.

Ah yes that's fine, I will be doing loads of hours at home as usual!