Deepa, just asking for tough words here will not really help much. Get him a few dictionaries, the latest versions that is, assign him tasks like reading and absorbing a few words form each and then writing them down without looking in the book. such tasks will help him learn spellings and their meaning more quickly than anything else.
"I am free of all prejudice. I hate everyone equally." - W. C. Fields :)
Just go through the link to see Indian-Americans who won this
http://in.news.yahoo.com/photos/indian-americans-who-won-spelling-bee-crown-slideshow/;_ylt=AmjA_htO3SZ.FCsGLIqpdk7GscB_;_ylu=X3oDMTM3OHM0N2s1BG1pdAMEcGtnAzY0ZTUyNmNlLTlkZmItM2UzMC05Y2YwLWI5ZmJhYTkxZGVlNwRwb3MDMQRzZWMDZW5kX3NzBHZlcgM4ODRmOTg4Mi1hYmRmLTExZTEtOGQ3Zi00NTU3M2NhYzkxODk-;_ylv=3
