This is the 2192nd most frequent Turkish word.
okulu
"The school" (possessive or accusative form of "okul").
In this sentence, 'okulu' is used as an object of the verb 'temizlemek', marked by the accusative case in Turkish.
Öğrenciler sabah okulu temizlemeye başladı.
The students started cleaning the school in the morning.
Here, 'okulu' serves as the object of the verb 'sevmek', again in the accusative case to indicate the school being loved.
Okulu çok sevdikleri için her gün erken gidiyorlar.
They go early every day because they love the school very much.
The word 'okulu' appears in the accusative case meaning 'the school', highlighting the goal of completion in the context.