Be allowed to - Be able to - Be supposed to

Here you have some links that you can use to practice Modal Verbs.

BE ALLOWED TO:

http://www.bbc.co.uk/worldservice/learningenglish/flatmates/episode101/languagepoint.shtml

BE ABLE TO:
http://www.autoenglish.org/translations/tr.beableto.pdf

BE SUPPOSED TO:
http://www.cristinacabal.com/intermediate/besupposedto.htm

A review of modals : http://www.esl-lounge.com/student/grammar/3g38-modal-signs.php