v3.23.3
Stockholders' Equity
 9 Months Ended
Sep. 30, 2023
Equity [Abstract]  
Stockholders' Equity Stockholders’ Equity
Common Stock
As of September 30, 2023, the Company was authorized to issue 205,000,000 total shares of capital stock, consisting of 200,000,000 shares of common stock and 5,000,000 shares of preferred stock. As of September 30, 2023, there were 81,630,808 shares of common stock outstanding, and the Company had reserved a total of 49,302,290 of its authorized shares of common stock for future issuance as follows:
Shares Reserved for Future Issuance
Outstanding restricted stock units5,498,359 
Outstanding performance restricted stock units1,946,407 
Outstanding stock options4,744,465 
Reserved for convertible senior notes37,113,059 
Total shares of common stock reserved for future issuance49,302,290 
Stock-Based Compensation
The Company maintains two stock-based compensation plans: the Amended and Restated 2014 Equity Incentive Plan (the “2014 Plan”) and the 2008 Stock Incentive Plan (the “2008 Plan” and together with the 2014 Plan, the “Stock Plans”). Upon the effective date of the 2014 Plan in January 2014, the Company ceased using the 2008 Plan to grant new equity awards. The shares available for future issuance under the 2014 Plan increased by 3,916,733 and 3,782,719 on January 1, 2023 and 2022, respectively, pursuant to the automatic share reserve increase provision in the 2014 Plan.
The Company also has a 2017 Employee Stock Purchase Plan (the “ESPP”). During the second quarter of 2023, shares available for purchase under the ESPP increased by 2,000,000 shares, pursuant to an amendment to the Company’s ESPP to increase the number of authorized shares available under such plan. As of September 30, 2023, 1,917,341 shares remained available for purchase under the ESPP.
The following table presents stock-based compensation expense related to the Stock Plans and the ESPP, contained on the following line items on the Company’s condensed consolidated statements of operations and comprehensive loss for each of the periods indicated.
 Three Months Ended
September 30,		Nine Months Ended
September 30,
 2023202220232022
 (in thousands)
Curriculum and teaching$37 $59 $128 $155 
Servicing and support2,257 3,061 7,773 11,741 
Technology and content development737 1,288 4,354 7,785 
Marketing and sales1,436 1,013 3,959 4,861 
General and administrative5,973 10,546 19,772 38,198 
Total stock-based compensation expense$10,440 $15,967 $35,986 $62,740 
Restricted Stock Units
The 2014 Plan provides for the issuance of restricted stock units (“RSUs”) to eligible participants. RSUs generally vest over a three- or four-year period. The following table presents a summary of the Company’s RSU activity for the period indicated.
 Number of
Units		Weighted-
Average Grant
Date Fair Value per Share
Outstanding balance as of December 31, 20224,739,861 $14.24 
Granted*4,080,159 6.45 
Vested(2,684,619)14.74 
Forfeited(637,042)10.69 
Outstanding balance as of September 30, 20235,498,359 $8.62 
*
Includes 215,054 RSUs issued pursuant to an inducement award outside of the 2014 Plan.
The total fair value of RSUs vested during the three months ended September 30, 2023 and 2022 was $2.8 million and $6.7 million, respectively. The total fair value of RSUs vested during the nine months ended September 30, 2023 and 2022 was $15.9 million and $23.9 million, respectively. The total compensation expense related to the unvested RSUs not yet recognized as of September 30, 2023 was $37.6 million, and will be recognized over a weighted-average period of approximately 1.9 years.
Performance Restricted Stock Units
The 2014 Plan provides for the issuance of performance restricted stock units (“PRSUs”) to eligible participants. PRSUs generally include both service conditions and market conditions related to total shareholder return targets relative to that of companies comprising the Russell 3000 Index and/or conditions based on the Company’s internal financial performance achieving predetermined targets. The terms of the performance restricted stock unit grants under the 2014 Plan, including the vesting periods, are determined by the Company’s board of directors or the compensation committee thereof.
During the first quarter of 2023, as part of its annual equity award cycle, the Company awarded 1.4 million PRSUs with an aggregate intrinsic value of $12.2 million. The PRSU award agreements provide that the quantity of units subject to vesting may range from 150% to 0% of the granted quantities. For the first performance period, which began on January 1, 2023 and ends on December 31, 2023, the quantity of units eligible to be earned ranges from 130% to 0% depending on the achievement of internal financial performance-based targets, which are established annually. Additionally, the actual number of PRSUs earned may be adjusted upward or downward by 20% based upon the Company’s total shareholder return (“TSR”) performance compared to the Russell 3000 Index’s TSR performance over the same period. If the Company’s absolute TSR is negative, the TSR multiplier cannot exceed 0% and the achievement percentage based up on the internal financial performance-based targets is capped at 125%. The grant date fair value of the PRSUs granted in the first quarter of 2023 includes the fair value of the TSR-performance component of the award, which was determined using a Monte Carlo valuation model, and was $0.39 per share.
The following tables present a summary of (i) for the nine months ended September 30, 2023, the assumptions used for estimating the fair value of the TSR-performance component of the PRSUs, (ii) for the nine months ended September 30, 2022, the assumptions used for estimating the fair values of the PRSUs subject to market-based vesting conditions and (iii) the Company’s PRSU activity for the period indicated. As of September 30, 2023 and December 31, 2022, there were 1.3 million and 1.0 million outstanding PRSUs for which the performance metrics had not been defined as of each respective date. Accordingly, such awards are not considered granted for accounting purposes as of September 30, 2023 and December 31, 2022, and have been excluded from the tables below. No PRSUs were granted during each of the three months ended September 30, 2023 and 2022.
 Nine Months Ended September 30, 2023
Risk-free interest rate4.68%
Expected term (years)1.00
Expected volatility108%
Dividend yield0%
Weighted-average grant date fair value of the TSR-performance component
$0.39
 Nine Months Ended September 30, 2022
Risk-free interest rate
0.39% – 1.88%
Expected term (years)
1.00 – 3.00
Expected volatility
49% – 97%
Dividend yield0%
Weighted-average grant date fair value per share$18.67
 Number of
Units		Weighted-
Average Grant
Date Fair Value per Share
Outstanding balance as of December 31, 20221,651,864 $22.74 
Granted1,176,077 9.55 
Vested— — 
Forfeited(881,534)19.33 
Outstanding balance as of September 30, 20231,946,407 $16.04 
The total compensation expense related to the unvested PRSUs not yet recognized as of September 30, 2023 was $4.9 million, and will be recognized over a weighted-average period of approximately 1.2 years.
Stock Options
The Stock Plans provide for the issuance of stock options to eligible participants. Stock options issued under the Stock Plans generally are exercisable for periods not to exceed 10 years and generally vest over a three- or four-year period.
The following tables summarize the assumptions used for estimating the fair values of the stock options granted for the periods presented. No stock options were granted during the three months ended September 30, 2023.
Three Months Ended
September 30, 2022
Risk-free interest rate
3.0%
Expected term (years)
5.78
Expected volatility
79%
Dividend yield0%
Weighted-average grant date fair value per share$7.78
Nine Months Ended
September 30,
20232022
Risk-free interest rate3.6%
1.9% – 3.0%
Expected term (years)5.69
5.63 – 5.78
Expected volatility87%
75% – 79%
Dividend yield0%0%
Weighted-average grant date fair value per share$4.93$7.02
The following table presents a summary of the Company’s stock option activity for the period indicated.
 Number of
Options		Weighted-Average
Exercise Price per
Share		Weighted-Average
Remaining
Contractual Term
(in years)		Aggregate
Intrinsic
Value
(in thousands)
Outstanding balance as of December 31, 20225,195,538 $25.28 5.88$78 
Granted66,910 6.76 8.50
Exercised(17,166)6.38 0.65
Forfeited(169,427)10.80 
Expired(331,390)19.55 
Outstanding balance as of September 30, 20234,744,465 26.01 4.75— 
Exercisable as of September 30, 20233,511,374 $30.56 3.79$— 
The aggregate intrinsic value of options exercised during the nine months ended September 30, 2023 and 2022 was $0.1 million and $3.2 million, respectively.
The total compensation expense related to the unvested options not yet recognized as of September 30, 2023 was $8.6 million, and will be recognized over a weighted-average period of approximately 1.4 years.