"Each year, hundreds of words are dropped from the English language. Old words, wise words, hard-working words. Words that once lived meaningful lives but now lie unused, unloved, and unwanted. Today 90% of what we write is communicated by only 7,000 words. You can change all that. Help save the words!"
This quote is taken from www.savethewords.org, a whimsical site that allows readers to register and adopt words. When you click on a word, you are given the definition. If you choose to adopt it, you promise to "use it in conversation and correspondence to the best of your ability." There is also an option to get a word a day sent to you. This is a site best monitored by you, the upper-elementary teacher, because the words are pretty complex. You could choose one that suites your class and the subject matter on which you are currently working. Have fun with it!