I've worked with Magic & Puppets since I was literally, in diapers and throughout my school life it never really hurt me all so much (other than pissing off some teachers here and there). On the other hand, my step son loved puppets & vent work but his own insecurities and ADD issues caused an awkwardness and so kids were kids and made fun of him for playing with dolls...
It goes back to what's been said already; your own sense of guts/audacity and the presentation/context. My buddy Joel & I were quite the hit in the lunch room during High School and I was a key part at my church, using both, Magic & Puppets as part of a Sunday School program for the younger kids (Yes, I used to be a serious Bible thumper. . . which gave me more grief in school than the magic & puppets ever did).
BACK TO THE OP. . . I wouldn't chance a talent show unless you have a minimum of two months lead time; time to create a solid act/series of routines that look good, that you feel confident as well as comfortable with & about, and that you know for a fact, you can do flawlessly. My first dove act was created when I was about 14 and it sucked, but I still did it. Two years later it was winning awards. . . so be willing to fail but learn from each failure so you can improve on what you're doing, how you do it, etc. understanding that sometimes you age can be a negative but only because of the material you've chosen. . . there's been a lot of kid magicians far younger than you who've won numerous talent programs, so keep that in mind as well.
Best of luck!