(This posting includes a handout which you are welcome to use with your students.)
One reason that ESL students often take so much time reading a passage is because they think that they need to understand all the information. As a result, many of them tend to cover a text in translation of every word that they are not familiar with. We have often heard of international students staying up until 2 a.m. trying to complete reading assignments in their academic courses.
This can change if they know in advance the purpose of the reading assignment.