This seems like a nice temporary solution to your stutter. Not gonna lie I might've done the same thing. At the same time I hope you do not apply these "outs" to every aspect of you public speaking opportunities. By not speaking, a stutter only gets worse over time. We can't overcome it by hiding it! I recommend you let your class and professor know that you have a stutter. This way in the case you ever have to speak to them normally, they won't be confused and may be more patient. Easier said than done I understand.