Brief Description of the Site:
This site has fairly difficult exercises intended for "pre-intermediate to high-intermediate" level learners who have a fairly high reading level. One nice feature is the animated tutorials, such as how to form a question by reversing noun and verb (toys are expensive / are toys expensive?) It is a very comprehensive site, with many exercises on a variety of topics.
How to use the site:
Ask your ESL students to start with the quiz that determines their level and helps them pinpoint errors. There's help to understand and correct the errors, after which they'll be able to select from a variety of related activities from a large menu of tutorials on using correct forms of English grammar from tenses to parts of speech to vocabulary and more. One exercise, about booking an airline flight, requires the user to add [There Is, There Are, Is There, Are There] into appropriate places in a "conversation."
Juliana Luna Freire