Notebooks and backpacks appear in stores while summer is still at its height, well before any school year begins. The timing is set by inventory that was committed a year in advance and by the far larger season waiting behind it.
The order was placed the previous summer
Seasonal merchandise is bought on long lead times. Quantities, designs and prices are agreed with suppliers roughly a year ahead so factories can schedule production and ocean freight can be booked.
By the time the goods land, the retailer holds a fixed quantity that cannot be adjusted. Nothing about the plan can respond to how demand actually develops.
Given that, starting early adds selling weeks at no extra cost, and selling weeks are the only variable left.
Shelf space is committed to what comes next
Retail floor space is planned as a calendar. Every square foot has a scheduled occupant, and the seasonal area turns over several times a year.
Back-to-school occupies that space until it must be handed to Halloween, which in turn hands it to the holiday season. Those dates are set centrally and do not move.
The season therefore has to be effectively finished before the following one arrives, which pushes its start date backwards into the summer.
Early buyers behave differently from late ones
Shoppers who buy in July are stocking up on basics, buying to a list and comparing prices carefully across stores.
Those buying in the last week before term are replacing what was forgotten, are under time pressure and are much less price sensitive.
Retailers price to that difference, running the sharpest promotions early to establish where the household shops, then holding prices firmer as the season closes.
Sales tax holidays anchor the peak
Many states suspend sales tax on qualifying school items for a set weekend, and those dates are known well in advance.
Retailers stock and advertise towards that weekend, since it concentrates demand into a few days and draws shoppers across state lines.
The season has to be fully set before the holiday begins, which pulls the whole timeline earlier again.
The markdown clock runs from the start date
Once the season opens, the merchandise is on a schedule of planned reductions that ends with clearing whatever is left.
Leftover school supplies keep well and could theoretically be held for next year, but the space and working capital they occupy cost more than the margin recovered.
So the goods are cleared rather than stored, which is why the deepest discounts land in the weeks after term has already started.