I'm wondering If there is a difference in use between "Needn't" and "Don't need". My language teacher says there's a difference between these verbs and as a modal verb "need' in the negative form when we want to give permission to someone not to do something can only be used as "Needn't". Is he right about this? Any help is more than welcome!
Thanks in advance :)
Here is a link to a very complete explanation: