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.

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