Students should first learn the words that are more commonly used. For example firstly it’s better to learn “disease” than the various diseases: flu, diabetes, diarrhea, etc.
Abridged readers and books can have a certain number of new key words, obviously increasing according the level goes up and gets more demanding.
Try your student read readers and books a bit above their level, and so they’ll actually be able to learn more interesting and commonly-used words. / Photo from: man-reading www richymiddleclass com