I have always wondered why a service like this doesn’t already exist. As they grow, children leave in their wake a stockpile of unwanted and outgrown clothing, a treasure trove for other moms. Sometimes, they shoot up so fast that clothing is only worn once or twice before it’s discarded.

Thredup, an online consignment store for kids, was founded on the premise that one parent’s trash is another’s treasure. Today, the Bay Area startup announced it was selling at a rate of $1,000 items a day and is projected to sell 100,000 new or like-new items in the Back-to-School shopping rush at the price range of $1.99 to $39.99.

Back in 2009, the site was initially conceived of as a clothing swap. Parents wanted to buy and sell directly through the site, so the team shifted to an online consignment this spring. The strategy seems to be working, with the company reporting 50 percent month-over-month growth since March.

To help parents sort through an enormous inventory of clothing, the company also announced it would bring on a new executive, John Voris, the former VP of Operations Engineering at Netflix and new board member Andy Rendich, former Chief Service and Operations Officer at Netflix.

“What’s really powerful from a recommendations stand-point, is that we know what items your kids have outgrown and how often kids outgrow clothes,” said Voris, thredUP’s new Chief Operations Officer, in an interview with VentureBeat. “We can harness that data to serve up powerfully personalized brand, size and style recommendations at just the right time.”

How does it work? Order a Thredup ‘clean out’ bag online and it comes to your door. Fill it with outgrown kids clothing, and put the bag on your doorstep with other outgoing mail. Thredup’s CEO James Reinhart told me that clothing on Thredup sells for anywhere between 40 percent and 80 percent lower than retail prices. To maintain high-quality, the team inspects all clothing, before it can be sold on the site.

The company has raised $8.7 million to date, with the first round led by Trinity Ventures and the second by Redpoint Ventures.