Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 158,072	$ 79,878
Marketable securities	122,729	205,402
Accounts receivable, net of allowance for doubtful accounts of $48 and $146 as of December 31, 2020 and March 31, 2021, respectively	35,582	40,721
Deferred costs	16,149	14,077
Prepaid expenses and other current assets	18,666	14,993
Total current assets	351,198	355,071
Property, equipment and software, net	21,080	18,644
Operating lease right-of-use assets	20,276	21,622
Intangible assets, net	10,313	10,570
Restricted cash	2,548	2,548
Other assets	9,407	9,169
Total assets	414,822	417,624
Current liabilities:
Educator partners payable	41,360	39,005
Other accounts payable	9,813	12,897
Accrued compensation and benefits	8,354	12,997
Operating lease liabilities, current	7,973	7,926
Deferred revenue, current	85,254	76,080
Other current liabilities	5,052	4,739
Total current liabilities	157,806	153,644
Operating lease liabilities, non-current	16,676	18,305
Other liabilities	623	644
Deferred revenue, non-current	3,513	4,562
Total liabilities	178,618	177,155
Commitments and contingencies (Note 12)
Redeemable convertible preferred stock:
$0.00001 par value - authorized, 76,420,805 shares as of December 31, 2020 and March 31, 2021; issued and outstanding, 75,305,400 shares as of December 31, 2020 and March 31, 2021; and aggregate liquidation preference, $464,036 as of December 31, 2020 and March 31, 2021	462,293	462,293
Stockholders’ (deficit) equity:
Common stock $0.00001 par value - authorized, 162,000,000 and shares as of December 31, 2020 and March 31, 2021, respectively; issued and outstanding, 40,301,290 and 43,193,216 shares as of December 31, 2020 and March 31, 2021, respectively
Additional paid-in capital	140,803	126,408
Treasury stock—at cost 2,747,938 shares as of December 31, 2020 and March 31, 2021	(4,701)	(4,701)
Accumulated other comprehensive income	23	20
Accumulated deficit	(362,214)	(343,551)
Total stockholders' deficit	(226,089)	(221,824)
Total liabilities, redeemable convertible preferred stock, stockholders’ deficit	$ 414,822	$ 417,624