Shaykh Ibn Uthaymeen was asked:
Oh Virtuous Shaikh, May Allah preserve you [this was before the Shaikh’s death, may Allah have mercy upon him]. [What is the ruling] in regards to a teacher leaving early after finishing fifth or sixth period after completing all his scheduled classes for the day, even though period six and seven remain in the school day?
“This is according to the system of the school. If the system prevents him from leaving except at the end of the school day, then it is a must for him to stay, even if he does not have work. If the system allows him to leave after he completes his classes, then he can leave”.
[Fataawa Noor ‘ala Darb no. 640]
Faisal Ibn Abdul Qaadir Ibn Hassan