http://www.sortfix.com/ "start dragging - stop typing". How many times are EFL students frustrated because they simply don't have the vocabulary to refine their websearches.
Sortfix may just be the search engine to solve the problem.
A basic search on SortFix returns a results page which includes 4 boxes or "baskets". The first basket contains "power words" and "power phrases" (relevant keywords and phrases) the second basket contains the original keyword. In order to refine the search all we need to do is drag relevant words or phrases from the first basket into the second basket. There is a 3rd basket entitled "Remove" any results containing words dragged into this basket will be excluded from the search results. The 4th basket the "dictionary" may be useful for more advanced EFL students, however the definitions are too difficult for elementary. Clicking on the "more options" link will allow you to add further functions to the search.
The SortFix help page includes explanations and videos which demonstrate the different functions.