Updated from 11 a.m. ET with new information

NEW YORK ( TheStreet) -- Retailers that still report monthly same-store sales had mixed results for the month of July. The teen segment in particular reported results below expectations, fueling the argument that the back-to-school selling season, the second-largest sales season behind holidays for retailers, will be disappointing.

Of the 11 companies that are tracked by Thomson Reuters, same-store sales have come in below Wall Street expectations, registering 3.9% growth, compared to an estimate of 4.4%, yet above the 1.4% sales growth in the year-earlier period. Excluding drug stores, July same-store sales registered 3.3% growth versus the 3.9% estimate.

Gap ( GPS) said late Thursday that July same-store sales data rose only 1% for the period, just short of analysts' average estimate of 1.6% and significantly below the 10% comparable sales growth it reported last year.

Gap said net sales for the second quarter rose 8% compared to a year earlier to $3.87 billion. Net sales for the four-week period ended Aug. 3 rose 5.6% to $1.12 billion.

Gap upped its guidance for the second quarter. It expects diluted earnings per share between 62 cents and 64 cents a share. Analysts on average expected the company to earn 59 cents a share on $3.8 billion of revenue.

Shares were falling 1.4% to $44.90 after the markets closed.

Also see: Retailers Brace for Lower Back-to-School Sales

July sales for Costco Wholesale ( COST), the biggest company that still reports monthly sales, also came in below the average analyst estimate. Shares closed 1.6% to $117.39.

The Issaquah, Wash.-based company reported net sales of $7.87 billion for the four weeks ending August 4, up 7% compared to July 2012.

Comparable sales for the four-week period rose 4% vs. 5.1% expected by analysts. Excluding changes in gas prices and foreign exchange rates, the company posted comparable sales of 5% for the month.

On the other hand, L Brands ( LTD), the parent company to Victoria's Secret, Bath & Body Works and La Senza, posted comparable store sales that were above expectations, boosted by strong comps at Bath & Body Works and La Senza.

L Brands' net sales for the four weeks ending August 3 rose 4.4% to $678.4 million vs. the 2012 four-week period that ended on July 28, 2012.

The company reported overall comparable store sales increase of 3% for July versus the 1.5% expected by analysts. July sales rose 6% at Bath & Body Works compared to expectations of 0.5% growth. Similarly, sales rose 9% at La Senza vs. the expected 1.4%, according to Thomson Reuters.

L Brands raised its second-quarter earnings guidance by 5 cents above the high end of the range previously given. The company expects to report earnings per share of approximately 60 cents on August 21 vs. its previous guidance of 50 cents to 55 cents, above last year's adjusted earnings result of 50 cents a share.

Shares surged 5.2% on Thursday to $60.25.

Overall though, the teen segment is having a tough time, suggesting that back-to-school sales will be weaker than normal.

July same-store sales growth at The Buckle ( BKE) narrowly missed estimates, coming in at 2.1% vs. the expected 2.3%.

That said net sales for the four-week period ending Aug. 3 jumped 16.7% to $77.2 million compared to last year, the company said Thursday.

Shares closed up 0.6% to $54.13.

Zumiez ( ZUMZ) on Wednesday said July net sales jumped nearly 20% to $56.1 million, but the company's comparable store sales rose just 0.8% compared to the 1.7% growth expected by Wall Street and significantly lower than the 7.5% sales growth in July 2012.

The stock closed up 5.3% higher to $28.44.

American Apparel ( APP) said net sales rose 5% to $57.6 million for the four-week period ending July 31. Comparable sales rose 8%, which included a 6% increase in same-store sales and a 23% jump in online sales. Still the 6% same-store sale jump was considerably below the 19% rise American Apparel saw in the year-earlier period.

"As we enter August, we anticipate continued strength in our sales channels and we are looking forward to back-to-school, Halloween and holiday selling season," Chairman and CEO Dov Charney said in a statement.

Shares fell 2% to $1.90. American Apparel will release its second quarter earnings results on Monday.

The results coincide with retailers like American Eagle Outfitters ( AEO) and Aeropostale ( ARO) reporting preliminary quarterly earnings results this week below Wall Street expectations.

Aeropostale issued a release on Thursday saying that based on lower-than-expected sales and margins for the quarter, its second-quarter loss will be in the range of 42 cents to 44 cents per diluted share. Analysts, according to Yahoo! Finance had expected the company to report a loss of 17 cents a share.

The loss includes 19 cents related to lower-than-expected income tax benefit and charges related to store asset impairments as well as an accounting change to its stock-based compensation plan.

Sales slumped 6% for the quarter to $454 million, Aeropostale also said. Comparable sales, including the e-commerce channel, decreased by 15% over last year, the company said.

Aeropostale shares fell 4.2% to $13.54.

"Our performance was driven by an increase in promotional activity as we navigated through balancing our assortment, weak traffic trends and a challenging retail environment, particularly during the July selling period," CEO Thomas P. Johnson said in a statement. "As we reposition the Aeropostale brand, we believe our current merchandise assortment is more fashionable and relevant. Our entire organization is focused intently on accelerating customer adoption and regaining market share."

The two teen retailers' pre-announcements makes clear that "mall traffic and apparel consumption is down and earnings at apparel retailers are under pressure," Stifel analyst Richard Jaffe writes in a research note. It also implies that "while promotions have been aggressively used in July, the impact on sales has been limited while margins and earnings have suffered for some retailers."

Jaffe notes that compared to a "highly successful" back-to-school season last year, which was driven by strong demand for bright color apparel trend, this year there is an absence of any strong fashion trend to drive consumers to make purchases.

Retailers are also feeling the pinch from a "shift in consumer spending preferences to non-apparel and big ticket purchases; specifically home, home furnishings, new cars and vacations," Jaffe writes. "This is setting the stage for a highly promotional August," which accounts for approximately 65% of back-to-school sales as key players "fight for market share in what appears to be a declining market."

-- Written by Laurie Kulikowski in New York.

To contact Laurie Kulikowski, send an email to: Laurie.Kulikowski@thestreet.com.

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