The best way for me to describe these two phrases would be to provide examples.
As one is past (were taken) and one is continuous (are taken).
It is very easy for a non-native English speaker to mix these two up.
“Were taken” would imply something which has occurred, which has happened already.
- The boys were taken home on Friday.
This sentence denotes that the boys had been taken home on Friday. The action is now complete.
“Are taken” describes something that is continuous. If we take the following two sentences and compare them, we can see how they actually differ.
- The boys are taken home every Friday.
This sentence denotes that the boys go home EVERY Friday. The action is continuous.