NEW YORK – Shoppers are holding off on back-to-school shopping, and those who delay long enough might be rewarded with some steep discounts from desperate retailers.

Revenue at stores open at least a year — an industry measure of a retailer’s health — rose 3.5 percent in July, the slowest pace since March, according to a tally of 11 retailers by the International Council of Shopping Centers. The figure, which excludes drugstores, was below a 5.5 percent increase in June.

Costco Wholesale Corp., typically a strong performer, was among the retailers reporting disappointing figures.

Many stores were already offering discounts and other come-ons to get shoppers to spend on the new shipments of fall clothing that started flowing in mid-July. But experts say even more deals are coming this month as stores try to boost sales for the back-to-school season, which runs from mid-July through mid-September.

“It was a lousy start,” said Walter Loeb, a New York-based independent retail consultant. “There will be even more discounts to make up the sales.”

Ken Perkins, president of RetailMetrics LLC, a research firm, agreed. “A vast number of shoppers are sticking to their shopping lists and are being very deal-driven,” he said.

Only a sliver of retail chains now report monthly sales figures, and the list doesn’t include Walmart and many other large chains. But Thursday’s tally adds to evidence that shoppers are being frugal about their purchases, particularly clothing. The back-to-school season is the second-biggest selling period behind the winter holidays.

On Monday, teen retailer American Eagle Outfitters Inc. slashed its second-quarter outlook because of weak traffic and sluggish sales of women’s merchandise. The teen retailer cited a highly promotional environment that only got tougher in July.

A clearer picture of how the back-to-school season is faring will emerge next week when major retailers like Walmart and Macy’s Inc. report their second-quarter financial results.

Overall, the back-to-school season faces a big challenge: Shoppers are shifting their spending away from clothing and toward bigger-ticket spending on their homes and cars because they have more credit available, said Stifel Nicolaus analyst Richard Jaffe.

He says they’re using this “fiscal freedom” to spend on the more expensive items, cutting into lower-priced impulse buys such as clothing. That has stores competing hard for dollars.