I wonder if you can ask the teacher to help you avoid that humiliation again and exempt you from public speaking? I've only had to do a couple of presentations throughout my life and then for some reason (which I'm happy for) I -never had any locks during them. Mostly my locking happens when someone asked me to repeat myself or somebody catches me off guard and I'm now thinking about my breath or my breathing and then everything comes out like the first part of 'COuld'