Early reports from U.S. retailers show modest revenue gains in July. Hot weather and deep discounts drove Americans into malls for summer bargains, but shoppers remained choosy. The sluggish spending raises worries about the health of the back-to-school season as Americans step up saving amid a stalling economic recovery.

As stores report their results Thursday, several chains had solid increases. Those include Costco Wholesale Corp. and Limited Brands Inc., but those figures are being compared with dismal spending in July 2009.

Teen merchants were among the hardest hit, with The Buckle Inc. and The Wet Seal Inc. suffering declines.

The figures are based on revenue at stores opened at least a year and are considered a key indicator of a retailers’ health.