When you decide to leave
There are many good reasons to move on: you have outgrown the role, the children's needs have changed, you are relocating, you want different hours, or the arrangement is simply no longer working. None of these require an apology. What they do require is professionalism.
Give as much notice as possible — two weeks is the minimum in most professional contexts, but in care work, four weeks is better when you can. The family needs time to find a replacement, and the children need time to adjust. Leaving with a week's notice — or worse, no notice — can damage your reputation in ways that follow you for years. Care communities are small, and families talk to each other.