I want to make it Read Only.
Can this be done?
Is it possible to allow only one reply per student in a discussion?
READ ONLY?: No Steve, sorry, not with standard Moodle.
There is a 2008 tracker item with code to fix this here: https://tracker.moodle.org/browse/MDL-12944 (Probably out of date now I guess)
ONLY ONE REPLY?. Pass, no idea. I presume just telling them to make only one post will not work.
-Derek
Please see Forum FAQ #12 'How can I close/archive a forum?' for how to make a whole forum read-only, if that helps - but not separate individual threads.
To make single threads read-only: well, you can do that with a pair of forums, one of which is read-only. You can move discussions to the read-only forum when you want to stop people adding to them.
I realise that this is not idea.
The OU's forumng module (https://moodle.org/plugins/view.php?plugin=mod_forumng ) does have a 'Lock discussion' feature that does exactly what you want.