There are so many English and foreign words that Japanese elementary school students already know. One EigoNoto.com activity, WYAN (Words You Already Know), shows how to activate this knowledge in the classroom.
The common word families used in the Eigo Noto are
food, sports, animals, colorsMy own experience shows that these are the groups of words most students know, as well. Keeping these groups in mind will help you the next time you need to prompt students to tell you some English words they already know.