It is up to the parents really. You can have your opinion but the decision ultimately comes down to the parents
Depends on who they are dating, if they're older than 14 then it should be illegal.
No one can tell a 13 year old that they can't date unless it's their parents and even then the child still doesn't have to listen.
13 year olds are independant people and dating is fully in their control.
They are too young.
Early relationships may contribute to a higher likelihood of promiscuity later on.
No they should be learning to mature their friendships so they are stronger before sex.