This is the 906th most frequent Hungarian word.
tudták
"tudták" = "they knew"
The word 'tudták' here is the past tense of 'tudni' (to know) in third person plural, indicating knowledge possessed by the students in the past.
A diákok már korábban tudták a választ.
The students already knew the answer before.
'Tudták' is used again as the third person plural past form of 'tudni', highlighting the lack of knowledge earlier.
Tegnap este még nem tudták, hogy mi történt.
Last night they still didn’t know what had happened.
In this sentence, 'tudták' is used as past ability in negative, expressing that they were unable to tell something because of being in a hurry.