As a primary school teacher, PVA stains are part of the territory. I know you have fixed it this time but if it happens again there is a way to get it out.
Soak the item in cold water overnight. The water must be cold as heat will set it in further. You can put in a little detergent but I don’t find it needs it at this stage. When you take it out, it will have either gone or be a ‘sludge’ depending on how thick the glue was. If a sludge, scrape off and soak a bit longer.
Wash the item on a cool wash in the washing machine and voila it should be gone!
I’ve only had this method fail once and that was on some suede type fabric so not surprising.