My parents are of different religions. My mother is a Jehovah's Witness and my dad is N/A. I was made to go to all the JW stuff until I was about 14. My parents let me decide if I kept going or not. I didn't.
It's definitely an adult decision, but that doesn't mean many aren't able to make a decision earlier. Nice, if your kid started reading a bible at home, what would your reaction be?