First, jury is a collective noun if you mean all the jurors as a group. I think this is how you are interpreting the sentence. Perhaps your teacher is thinking of the individual members in the jury, in which case she is correct.

But there is another problem. If we go with the collective point of view, then we have to change their to it. Maybe that’s why your teacher’s answer book gives ‘take’ as correct.

A better sentence would be “The jury members take their seats.”