Free rice. Educate and feed the world at the same time.

World Food Programme  (WFP.org)
This site operates with the objective of feeding the poor and also educating people.  A vocabulary site with words graded to 60 different levels. Sign up yourself or a class.  Make it a daily before class challenge.  Which class in your school can accrue the greatest amount of rice donated?
What is the process?
A word shows and you have to choose the correct synonym.  Acorrect word chosen and 10 grains of rice are given.  If you get it wrong it gives the correct answer and asks the same word later in the session.  This time youi will hopefully get it right.
The words adjust to your level.  They get harder as you get words right and will get easier if you get too many wrong.
When you get three words correct in a row you go up a grade. For each correct word the site gives 10 grains of rice to the poor through the World Food Programme (WFP.org).  The site remembers your grade  and your rice contribution. Advertisements show on the bottom the screen and this is what pays for the site and the rice.