1. Does High School Homework Increase Academic Achievement? Charlene Marie Kalenkoski Texas Tech University Sabrina Wulff Pabilonia U.S. Bureau of Labor Statistics June 24, 2014

2. Introduction Previous Research  High school homework improves students’ performance on math tests (Betts, 1996; Aksoy & Link, 2000; Eren and Henderson, 2008)  Studies of middle school students (Eren & Henderson, 2011) and college students (Stinebrickner & Stinebrickner, 2008; Grodner & Rupp, 2013) have found that homework improves students’ performance on math and other tests and first- semester GPAs.

3. Introduction Previous Research  These studies primarily used retrospective questionnaire data that provided information about assigned or completed homework during a typical week.  Exception: Stinebrickner & Stinebrickner (2008), but only examined students from one college.

4. Introduction Time-diary Data  Are more accurate  Are less subject to social desirability bias  May capture information about secondary activities that survey data do not  Usually do not include information on future outcomes

5. Contribution We use a nationally-representative time-diary data set that includes future outcome measures  Panel Study of Income Dynamics (PSID) Main interviews Child Development Supplements (CDS): 1997, 2002-2003, 2007-2008 Transition to Adulthood Surveys (TA): 2005, 2007, 2009, 2011

6. Contribution We merge in additional data on  School characteristics from the National Center for Education Statistics Common Core of Data (CCD)  Weather data from the National Climate Data Center (NCDC) of the National Oceanic Atmospheric Administration (NOAA)

7. Sample High school graduates who were enrolled in grades 9 through 12 in 2002-2003 or 2007-2008 (when the CDS time-diary data were collected)  805 respondents, including 438 females and 367 males

8. Outcome Variables Measures of Academic Achievement  High school GPA (ranges from 0 to 100)  College attendance by age 20

9. Explanatory Variables Homework Measures  Total weekly hours spent doing homework  Weekly hours spent doing homework as a primary activity  Weekly hours spent doing homework as a sole activity

10. Explanatory Variables Family Characteristics  Number of other household children under age 20  Average real family income over the 5 years prior to the time diary and its square  Indicators for whether the mother had a college degree and whether the mother’s education was missing  Indicators for whether the student lived with a single mother or in some other non-two-parent family arrangement

11. Explanatory Variables School Characteristics  Fraction of the respondent’s high school that was white (averaged over the respondent’s high school years)  Fraction of the respondent’s high school that was free- or reduced-price-lunch eligible (averaged over the respondent’s high school years)  Respondent’s high school’s student-teacher ratio (averaged over the respondent’s high school years)

12. Explanatory Variables Instruments: Indicator for whether the weekday diary day was a Friday Indicator for whether the weekend diary day was a Saturday Indicator for whether the diary was in a spring month Indicator for whether the student was older than the state minimum driving age at the time of the weekday diary Average precipitation in the county of residence on the weekday diary day

13. Select Descriptive Statistics Females (N=438) Males (N=367) MeanStandard Deviation MeanStandard Deviation High school GPA 83.4911.2978.3213.14 Attend college by age 20 0.900.87 Total homework 7.557.965.217.71 Primary homework 7.017.774.997.48 Sole homework 3.595.802.454.31

14. Differences in Average Hours Spent on Total Homework by GPA Above- Average GPA Below- Average GPA DifferenceP-value Female7.84 (7.32) 7.22 (8.64) 0.620.53 Male5.58 (7.26) 4.83 (8.01) 0.750.50

15. Differences in Average Hours Spent on Total Homework by College Attendance by Age 20 Attend College by Age 20 Not Attend College by Age 20 DifferenceP-value Female7.65 (7.95) 6.66 (7.69) 0.990.47 Male5.62 (7.80) 2.37 (4.15) 3.250.00

16. Econometric Analyses First set of analyses: Homework time (H) is treated as exogenous in the outcome equation.  Outcome equation is either Z = b 0 + b 1 *H + b 2 *X + u (High School GPA) or Y* = a 0 + a 1 *H + a 2 *X + e(College Attendance by Age 20) Y = 1 if Y* > 0 Y = 0 otherwise

17. Econometric Analyses Second set of analyses: Homework time (H) is treated as endogenous.  Jointly estimate each outcome equation with the following homework equation via limited information maximum likelihood: H = d 0 + d 1 X + d 2 W + γ  W includes variables that are highly correlated with H but not directly correlated with the outcomes (instruments)

18. The Effects of Homework Time on Achievement (Homework Treated As Exogenous) GPA (OLS)College Attendance by Age 20 (Probit) Female (N = 438) Male (N = 367) Female (N = 438) Male (N = 367) Total Homework 0.0669 (0.0825) 0.0602 (0.1434) -0.0018 (0.0020) 0.0074** (0.0036) Primary Homework 0.0802 (0.0874) 0.0408 (0.1409) -0.0021 (0.0020) 0.0073** (0.0036) Sole Homework -0.0109 (0.1129) 0.3784*** (0.1302) -0.0038 (0.0030) 0.0082** (0.0036)

19. The Effects of Homework Time on Achievement (Homework Treated As Endogenous) GPA (OLS)College Attendance by Age 20 (Probit) Female (N = 438) Male (N = 367) Female (N = 438) Male (N = 367) Total Homework 0.3498 (0.4028) 0.0358 (0.4784) -0.0140 (0.0397) 0.0100 (0.0584) Primary Homework 0.4372 (0.3961) 0.0190 (0.4860) -0.0128 (0.0388) 0.0053 (0.0560) Sole Homework 1.8184 (2.3868) 0.9372 (0.9096) -0.0087 (0.1424) 0.0525 (0.1560)

20. Conclusion When we treat homework as exogenous (our preferred specification) we find that  Homework as a sole activity has a small positive significant effect on GPA for males.  Homework has a significant positive effect on the probability of attending college by age 20 for males.

21. Conclusion When we treat homework as endogenous (non- preferred specification) we find that  All effects of homework disappear.