# Thirty of them at once > Teacher merchandise is apples and pun mugs. A sentence broken into a syntax tree on a blackboard is the actual work — decomposition, in front of a room, for the fourth time today. August 17, 2026 · https://justog.club/stories/teacher-classroom-shirt A sentence drawn as a tree on a blackboard, branch by branch, with the phrase being parsed reading `THIRTY OF THEM AT ONCE`. It's a grammar lesson and it's a description of the working conditions, and both readings are true. ## Why a diagram rather than a slogan? Because teaching is decomposition, and a diagram is what decomposition looks like. The job isn't knowing things. It's taking something whole, breaking it into parts a person can hold one at a time, and reassembling it in front of them — repeatedly, for different people, at different speeds. A syntax tree is literally that operation drawn out. So is a long division, a force diagram, a timeline, a periodic block, a sentence diagram. ## What makes the double reading work? The phrase being parsed is doing two jobs. `THIRTY OF THEM AT ONCE` is a valid sentence fragment to demonstrate on, and it's the fact of the job. Any teacher reading it gets both at the same time, and nobody else notices there was a second one. That's the most reliable structure in this whole area: [an image that reads as a graphic to strangers and as a memory to the right people](/stories/valentines-custom-gift). ## What's the chalk doing? Making it a record of a real board. Chalk texture — slightly smudged, uneven pressure, the ghost of something rubbed out — says a person wrote this by hand, once, quickly. A clean vector version of the same tree is a diagram about teaching; a chalk one is an afternoon. The smudge is the equivalent of [the misregistration on a riso poster](/stories/protest-poster-riso): evidence of production conditions. ## Does this work outside language teaching? Every subject has its diagram, and the format transfers exactly. - **Maths** — a long division laid out, or a proof's structure. - **Physics** — a free-body diagram with the forces labelled. - **Chemistry** — a mechanism with curly arrows. - **History** — a timeline with one date circled. - **Music** — a chord broken into intervals. - **Primary** — a phonics breakdown, which is the most affecting of the lot. The subject-specific version is what makes it a gift for *that* teacher rather than a teacher-shaped present. ## Can I use the school's name? The school's name and crest are the institution's, and schools do license them. The classroom is yours, though: a room number, a year group, a subject, or a nickname the department uses. Those are considerably more specific anyway — `ROOM 14` means something to the people who taught in it and nothing to anyone else. Same distinction that [lets you draw the building but not the crest](/stories/graduation-gift-shirt). ## Is this a gift or a self-purchase? Mostly a gift, and it's a hard category to buy for. Teacher gifts are famously generic — mugs, wine, apple-themed anything — because the giver usually doesn't know the subject well enough to be specific. A diagram from their actual subject fixes that with one piece of information, which a student or a partner can easily supply. The end-of-year version, with a year on it, becomes [a series worth collecting](/stories/anniversary-gift-custom). ## Does chalk print well? Yes, with the usual caution about the smallest labels. Chalk on a dark ground is high contrast and hard-edged enough to survive, and the texture is coarse rather than fine. The node labels on a tree are the risk — keep them few and large, and let the structure carry the reading. Fewer branches than a real board, drawn bigger. It still reads as a lesson. ## How do I get one made? Describe the diagram at [JustOG](/) — the subject, and the thing being broken down. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped. Designs other people have published are in the [shop](/shop). It parses correctly. It's also just true.