Legally a person is considered an adult in most states at either 18, or 21.
In other cultures it must vary. Children can believe the gospel before adulthood if God saves them. Most confessional baptists are not in a rush to baptize very young children. Young children say they believe many things, that as they grow older they change their mind on.
Some baptist parents are over-eager to baptize young children so they{ the parents can comfort themselves} that in their mind the child is now on His or her way to heaven. It is probably best to wait until the Holy Spirit saves the child first however.
We went into a fundamental baptist church once when my second son was 5yrs old. One of the deacons was talking to him and my son said he believed in Jesus. The deacon wanted to baptize him right away. We explained that we would prefer to wait until we had reason to believe that the Spirit had given him new life.
Laws are written to protect children in our society. At what age can someone drive? Drink? Give Consent for medical treatment? Get married? Sign a legal document?
Some day they will do all these things , but it is probably not good to allow them to while they are young and lack understanding.
Why push to tell your child -you are saved- you are a christian- you are a disciple- you can live a life pleasing to God just as you are- live up to your baptism- improve your baptism.... When more than likely they have not been regenerated yet! So you expect them to be, act, or live as a christian without the indwelling Spirit? In the stength of their flesh they will do no more than give an outward conformity to an external standard, when God will give a new heart. A false and fleshly "church member" is a hypocrite at best and a dried out dead formilist at their worst.
Cults indoctrinate their children, it is religion without the Spirit. Nobody here wants that for their children.
Baptists do not tell their children that much different than a presbyterian tells their children hopefully. Jesus saves sinners, Jesus saves His people.Jesus saves all who believe. All died in Adam.All In Christ live.
You {the child} live in a home with believing parents. If God is merciful to you , you also will believe and be saved as your parents were saved by God.
We { your parents} cannot save you. You must deal with God personally. We can only tell you the truth as it is In Christ. The promise of life is only to those who believe by a God given faith.
Anyone who remains seperated from God and dies without Christ will die in their sins.