Though by definition baptists agree that a person should be baptized only after confessing faith in Jesus Christ, there are several views on how old a believer must be, or should be, before such a confession can be trusted and acted upon. The views range, on the one end, from baptizing a confessing believer no matter how young to, on the other end, not baptizing them until they are practically independent from their parents.
I’ve linked to statements from solid churches that stand on opposite ends of this spectrum and to two other notable churches that fall more in the middle. There’s a summary of each view under the church’s name; you’ll want to follow the link to read more of their rationale.
Heritage Baptist Church , written by pastor Ted Christman:
For more than thirty years Heritage Baptist Church has been baptizing only those who give credible evidence of true conversion. There is nothing remarkable about that claim. It is simply a part of what it means to be a biblical Baptist church. What might be noteworthy, however, is the fact that for the same period of time we have been baptizing everyone who gives credible evidence of true conversion - including young people and children.
Capitol Hill Baptist Church , written by the elders:
While it is difficult to set a certain number of years which are required for baptism, it is appropriate to consider the candidate's maturity. The kind of maturity that we feel it is wise to expect is the maturity which would allow that son or daughter to deal directly with the church as a whole, and not, fundamentally, to be under their parents' authority. As they assume adult responsibilities (sometime in late high school with driving, employment, non-Christian friends, voting, legality of marriage), then part of this, we would think, would be to declare publicly their allegiance to Christ by baptism.
Grace Community Church , compiled from material by pastor John MacArthur and others:
Here at Grace Community Church, our general practice is to wait until a professing child has reached the age of twelve. Because baptism is seen as something clear and final, our primary concern is that when a younger child is baptized he tends to look to that experience as proof that he was saved. Therefore, in the case of an unre- generate child who is baptized--which is not uncommon in the church at large--baptism actually does him a disservice. It is better to wait until the reality to which baptism testifies can be more easily discerned.
Bethlehem Baptist Church , written by pastor David Michael:
It is our practice to wait until a child is at least age eleven before considering him for baptism. More importantly it is our practice to wait until there is evidence of regeneration and enough maturity to articulate the Gospel and give a credible profession of faith. For further consideration of this topic see “Why Wait? Four Practical Reasons for Withholding Baptism Until Children Are Older ” by Pastor David Michael.