Adding a script to node attaches to all children?

So I have a prefab which comprises a parent node and 4 children nodes.
I added a script to the prefab
The onLoad function of the script seems to execute as each of the children are setActive - as if the script is also attached to each child node.

a) is this normal behaviour
b) if so, how do I stop it?

Thanks

*** Updated ***
It actually seems as if the script itself is the node that is causing the script’s onLoad to run! What sort of recursive trip am I on?!

if I look in debug at the onLoad method, the first time it is called, the ‘this.node’ property is the correct node of the instantiated prefab. Then, the onLoad method is called again, this time the ‘this.node’ property seems to be the script itself?!

*** Updated again ***
Looks like when I dragged my script to the prefab, it added it as a child (as well as adding it as a script) - I deleted it from the prefab and now it seems to be ok…