Forum discussion subscription plugin
Local plugin for allowing email subscription to discussions (threads) and not the whole forum.
Discussion subscription can works together with full forum subscription, but the user will receive the same emails two times.
Discussion subscription supports also diggest if the user has enabled this option in his profile.
As a teacher, in the forum activity go to the settings block and click on "Discussion subscriptions" -> "Enable"
Once enabled, the users will be able to click on the "Subscribe to this discussion" in a discussion page.
Juan Leyva <http://twitter.com/#!/jleyvadelgado>