This is the 10531st most frequent Russian word.
виновными
"Виновными" means "guilty" (plural, instrumental case).
Here 'виновными' is used as a predicate adjective, describing the students in the state of being guilty as perceived by the teacher.
Учитель не считает студентов виновными за ошибки.
The teacher does not consider students guilty for mistakes.
In this sentence, 'виновными' is used in a passive voice construction as an adjective describing the state of people being judged as guilty.
Их признали виновными в краже.
They were found guilty of theft.
Here 'виновными' is used as an object complement, describing the state of the subject being perceived as guilty by the action of considering.