The seasonal peak makes this look like a seasonal search problem and it is not. The pages that carry August have to exist and mature through the rest of the year. Grade-level pages are the backbone: one per year group, with the items commonly required, the bundle, and copy about what changes at that grade. School-list pages, where a store serves particular districts and can hold their lists accurately, are unusually strong when maintained and damaging when stale, so only take that on with a process that keeps them current and a visible date on every page.
Item pages carry a different job. A list line specifies a thing precisely, so the page has to answer that specification exactly and rank for the way the list writes it rather than for a marketing title. That means the size, ruling, count and dimensions in text, and titles written in the shopper's words. Bulk and classroom pages carry the institutional queries, which are lower in volume, higher in value and far less contested than the consumer terms.
Technically, colours and pack sizes are variants of one product. Grade pages keep their URLs and get refreshed rather than republished, so the ranking history compounds year over year. Items out of stock during the peak stay live with a date instead of being hidden, because a parent will wait two days for the exact item a list requires. Site speed matters more here than in most niches, since traffic multiplies inside a fortnight.