I remember very well how I felt when I was a kid and got baptized at 13: I had made up my mind, I had decided to serve Jehovah, and no one could stop me. Anyone who would get in my way would be swiftly dismissed in the same way Jesus dismissed Peter before going through his ultimate sacrifice.
My point is: If you say no, or even sound like you are discouraging your kid, he will hear nothing.
So, you will need to walk with him and steer his direction, not hit the brakes.
First, you need to command him on wanting to be baptized. The fact that he wants to be and do good in his life is truly commendable. For that fact alone, you can be proud of him.
However, you are concerned about his ability to make an informed decision. Ask him to read the second baptism question and ask him why it is needed? Wouldn’t it be implied of derived from the first question? What was the previous second question? Why did they change it? Have him reflect on these things himself. Tell him you don’t want to hear: I don’t know. He can make researches for school, he should be able to make such research for the most important thing in his life.
In the end, it will come down to “it’s a legal contract with the watchtower”.
Then, ask him to make a research on how to make a wise decision when buying a used car. When he comes back, he should normally have steps like:
Validate the reputation of the business
- with current/previous customers
- with the government
- with the neighbors
- with the competitors
Validate the quality of the car by
- Getting a report on the car to know if it was in an accident before
- Get information on its previous owner(s)
- Scrutinize for defects yourself
- Try to drive it to see if you like it
Then, tell him that he should ignore disgruntled customers as they all have bad motives. The government has no idea what he is talking about. The neighbors are jealous and the competitors are outright lying. The car was in an accident, but the report is probably falsified. The previous owners were jerks but they don’t own the car anymore, so that’s too far into the past and every dent and rust you see…well, you are not focusing on the right thing, the motor. And no matter how you feel when you drive this thing, I am telling you how you are feeling: You are in the best car in the world, you are happy. You don’t feel this way? That’s because you are negative. Look how happy I am in it.
Then tell your kid: Here is what I want you to do: Take some time, like a week, and list a few things you don’t like about the society, or that you simply don’t agree with. I’d like to hear what disturbs you the most, and some little things that are simply annoying to you. Then, come back and well talk about these.
When he comes back to talk about these things, ask him why they should simply be ignored. You may also help him understand how important these things truly are. After all, if they were not important, ask him to casually talk about these things at the next meeting(s) with at least three different elders and see how they react. If the elders use the “wait on Jehovah”, ask them if it would be alright to talk with other JW at various times to know what they thought about it. If these things are not important, why would it matter? Oh, they could create division? Well, there are many things that are left to the conscience, are you telling me that simply talking about these things and how we feel about these could create division and we should not express ourselves AT ALL on the matter?
Then tell him: This is not a hypothetical question. I want you to do it for real. How are you feeling now? A little afraid? Why would this feeling come up for insignificant matters in a religion that has more love to spare than anyone else on the planet?
If you have doubt about this, you can put a hold on getting baptized to a later time. After all, wasn’t Jesus 30? Can you show me one scripture where a kid was baptized?
If I can think of my 13 year old self, that would have turned me off right there.