One needs to give presentation every alternate week in my college. To avoid any losing enough score I inform the invigilator beforehand that I stammer and that I might need more time than my other classmates to complete the presentation. Most of them are understanding so they give me the score that I deserve and don't judge me for how I speak and deduct 1 or 2 points out of ten sometimes when I speak for too long. But there are also those (2 out of 6 teachers) who deduct my score even if I inform them about condition. What I want to say here is that we shouldn't miss out on any opportunity to speak or do something just because we stutter, informing the other person about our impediment works out (if that person isn't an a**hole). Hope this helps