9 year old walked home alone without permission - what is an appropriate consequence?

My 9 year old (A) is not allowed to walk home from school on their own. A knows this. A few times over the past few weeks, A has come out of school and asked to walk with a friend, B, whose parents do allow them to walk on their own. We live on the same street as B and as I am walking with my other children, I'm usually only a few meters behind A and B all the way home.Today, A walked home with B without asking permission or telling me. I didn't see them come out the classroom door (I'm assuming they left when I was distracted with the other children) so I didn't know A had left school.School noticed I was still waiting and asked if A had not come out yet. The teacher searched the whole school and was clearly panicked and upset. I realised pretty quickly what must have happened and called B's parent to ask if A was with B. They called me back a few minutes later to confirm both children had arrived at B's house. A does not have a mobile phone or house keys, and will not have either until they start high school at 11.I have firmly (but calmly) explained to A why I was angry, scared and annoyed. I have told A that tomorrow, I expect the teacher will get an apology for causing her so much upset.I grew up with a parent who overreacted a lot and had I done this as a child, I'd have been spanked, grounded and probably more. I will not do what my parent did to me.However, this is the first real "naughty" behaviour I've ever had from A. A made a decision to walk home without telling me and asking first. A is still a child and didn't think about consequences but I feel this needs addressing and there needs to be consequences but I just don't know what. How would you handle this? via /r/Parenting https://ift.tt/2wvmWkw