Margot, the part where he knows he’s not supposed to follow her home — that is the part to hold onto. That is actually the most useful sentence in your entire letter, and I want you to sit with it for a moment before we go further.
In my experience with entities of this particular configuration — the height, the stillness, the oval or field placement, the absence of conventional facial features — the ones who understand and observe relational boundaries are almost categorically less concerning than the ones who don’t. A boundary acknowledged is a boundary that can be maintained. That is not nothing. That is, in fact, quite a lot.
Now. Two things I would suggest.
The first is practical: establish a consistent goodbye ritual for Isla at the school gate. Something small and repeatable — a phrase she says, a gesture, something that signals the visit is finished for the day. Children’s relationships with liminal figures benefit enormously from structure and clear endpoints. It gives the child agency, and in my observation it also communicates something to the entity itself — that there is a shape to the friendship, that it has a beginning and an end each day. You are not forbidding the friendship. You are giving it walls, which is what all friendships need. Ask Isla what she thinks would be a good goodbye. She will have an idea. They usually do.
The second — and I want you to trust me here — is to leave a single dried calendula flower at the base of that gum tree on a Thursday. Not a bunch. One. Don’t explain it to anyone, including Isla. This communicates acknowledgement without invitation, which is precisely the register you want.
(A brief aside: my calendula has come in extraordinarily well this season, which I mention because I’ve had three letters in the past month that have required it. There may be something in the air. There often is, in autumn.)
As for the teacher — Margot, I know. I know. The foreshortening comment in front of that drawing. But consider: Isla’s teacher has given her a safe, enthusiastic adult response to something Isla has chosen to represent on paper. Isla is not frightened. She is drawing. That is genuinely healthy, and the teacher’s obliviousness has accidentally protected that. Let it be. Enrol her in the art enrichment programme if it’s offered. The Tall Man and the perspective lessons are not mutually exclusive, and Isla, by the sound of it, is managing both with more composure than most adults I have corresponded with.
You are doing the right things by paying attention and by writing to me. Keep doing both.