Hmm, if your professor during the first day of class mistakes you for a high school student and ask what the hell are you doing in his higher English class and won't believe you even if you said you are a junior and have taken all prerequisites for that class, will that still be amusing?
I look younger than my age (turning eighteen in a couple of months), and still younger than most my batchmates by a year. Overall result I look like a high school student next to them.