School Start Age and Hyperactivity in Canadian children

School Start Age and Hyperactivity in Canadian childrenKelly Chen, Nicole Fortin, Philip Oreopoulos and Shelley PhippsThis research is being conducted as part of the Canadian Institute for Advanced Research (CIFAR) Programme on Social Interactions, Identity and Well-BeingWe thank CIFAR for funding support and Heather Hobson of the Atlantic Research Data Centre for vetting our output2MotivationAttention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed behavioural disorder among young children in many countries (Elder, 2010; Faraone, et al., 2003; Skounti et al., 2007)Secular trends hard to identify given changes in diagnostic practices, but dramatic increases apparent over past 40 years (Perrin et al., 2007)Current estimates suggest worldwide ADHD prevalence between 4 and 10 percent (Faraone, et al., 2003; Skounti et al., 2007; Spencer et al., 2007)

3Consequences of ADHD in Educational Context Score lower on math/reading testsMore likely to repeat a grade More behavioural problems at school(Currie and Stabile, 2006; Loe and Feldman, 2007)

** These present even for children with some symptoms of hyperactivity, even if not diagnosed or at clinical levels4School Start Age and HyperactivityElder (2010) presents evidence that children who are young within grade at school are more frequently diagnosed with ADHD 8.4 percent of those born in the month prior to state cut-off for kindergarten eligibility compared to 5.1 percent for those born in the month afterTeacher assessments of symptoms had strong association with relative child age; parent assessments only a weak associationSciotto et al., 2004 find that teachers are more likely to refer boys for ADHD

5Misdiagnosis not the Whole Story?Children who are young in class may feel frustration, be more tired, like school less, be less engaged and so become restless or inattentive?Well look at impact of school start age on symptoms of hyperactivity well below normal clinical levels, which can still connect to poorer educational outcomes (Currie and Stabile, 2006; Chen et al., 2011)6Research QuestionsAre Canadian children who are young relative to their class-mates more likely to exhibit symptoms of hyperactivity than their classmates?If so, are there gender differences in the extent to which this is true? Is there an impact of being young in class even controlling for pre-school hyperactive symptoms?7School Entering Rules in CanadaAcross provinces, children are admitted to school once a year, with eligibility determined by a single cut-off dateKindergarten not compulsory, but is normalCompliance rates very high (over 95% of children in correct grade in K through 3Each province (school board, in AB/SK) has the flexibility to set school entry datesRange from early September to March during1987-2004 8Cut-Off Dates for School Entry Sep. 1Sep. 30Dec. 1

Dec. 31Last Day of Feb.Mar. 1ABCalgary School District

QCNSMB(87-96)BCSKMB(97-04)ONNBNL

AB

LethbridgeRed Deer LloydminsterGrande PrairieWetaskiwinABMedicine Hat School DistrictAB

EdmontonSchool District9Two Research Strategies10Regression DiscontinuityCompare children within provinces who are born just before or just after school start date (e.g., Nov/Dec versus Jan/Feb babies, when Dec 31 is cut-off)Difference in DifferenceCompare children of exactly the same age in months living in provinces with different start dates so that one may be youngest in class while another is oldest in class (e.g., Nov babies who are young with Dec 31 cut-off but old with a September 30 cut-off)

DataStatistics Canadas National Longitudinal Survey of Children and Youth (NSLCY)First cycle begins in 94/95 with data collection occurring at two year intervalsPool data from cycles 1 through 8, 1994 through 2008

11Basic Analytical Sample12Children aged 4 -9 yearsIn Kindergarten through Grade 3Who attended public (or publically funded) schoolsWith parent report of province of residence when 4/5 years old and have not moved inter-provincially since

Hyperactivity IndexHow often would say this child Cant sit still or is restlessIs easily distracted, has trouble sticking to an activityCant concentrate, cant pay attention for longIs impulsive, acts without thinkingHas difficulty waiting for his turn in games or groupsCannot settle to anything for more than a few minutesIs inattentive1= Never or not true; 2= Sometimes or somewhat true; 3=Often or very trueScore ranges from 0 to 1413Research Strategy I.Regression Discontinuity

Hyperi = + Youngi + f(bdi-ci) + 1 Province i + 2 Cycle i + 3 Grade i + Xi + i

Compare children within a province and grade who are born just before and just after the legal cut-off date14Illustration of RD approach15

Table 1. Regression Discontinuity Estimates of the Effect of School Starting Age on Hyperactivity Scores. 4 to 9 year olds.Sample Mean(1)(2)(3)(4)(5)(6)Young0.530**(0.231)0.477**(0.226)0.573***(0.199)0.562***(0.199)0.661***(0.150)0.714***(0.149)2 month windowN=82934.099xx3 month window N=124914.100xx6 month windowN=248784.095xx+ Covariatesxxx16Boys and Girls Compared17

Table 2. Regression Discontinuity Estimates of the Effect of School Starting Age on Hyperactivity Scores. Boys vs Girls.BoysGirlsMean(1)(2)(3)Mean(4)(5)(6)Young0.681*(0.345)0.935***(0.295)0.910***(0.217)0.252(0.25)0.173(0.220)0.523***(0.178)2 month window4.55x3.64

x3 month window4.55

x3.61

x6 monthwindow4.62x3.57x+ CovariatesxxxxxxN4133618412270403259551187618Research Strategy II.Compare children of exactly the same age in provinces with different cut-offs, so that in one province, the child is young in class while in the other, he/she is old in classIf born in 6 months prior to provincial cut-off

19Some Provincial Variation in Young Variable for DID estimationSept 1Sept 30Dec 31CalgaryQuebec, NSBC, ON, NB, NL JanuaryFebruaryMarchYoungAprilYoungYoungMayYoungYoungJuneYoungYoungJulyYoungYoungYoungAugustYoungYoungYoungSeptemberYoungYoungOctoberYoungNovemberYoungDecemberYoung20Hyperactivity Scores for April to June babies with Oct to Dec babies21DID Estimation22

All regressions control age in months (have done everything using higher order terms in age in months with no change in findings)Table 4. Difference-in-Difference Estimates of the Implications of Being Young in Class for Hyperactivity Symptoms. Boys + Girls

BoysGirls(1)(2)(3)Young0.486***0.124)

0.515***(0.157)0.453***(0.089)Boy1.057***(0.035)

N24146

1227011876Other covariates included: (Log of) Family Equivalent Income, Parental Education, Family Structure, Immigrant Status, Childs Health, Cycle Dummies. Cubic age in months.23Robustness Checks24Exclude children not in correct grade (very few; no noticeable change in results)Include all children (e.g., in private schools same results, only very slightly smaller estimated magnitudes)Check strategic timing of births? No apparent patternOther reasons for jumps at cut-off date? Regress each covariate on young (only mother higher education marginally significant positive)

BC

Quebec

Ontario

NS25Research Questions about Pre-school hyperactivity26Does starting school young still increase hyperactivity once we control for pre-school symptoms?Do more hyperactive children have a particularly difficult time being young in class? Are there gender differences?

27

28Control for pre-school hyperactivity in both RD and DD models Use longitudinal sample of children observed at age 2/3 as well as at ages 4 through 9Consider both linear pre-school hyperactivity scale and high hyperactivity29Table 5. Controlling for Pre-school Hyperactivity in Regression Discontinuity Models. 3 month window.Boys + Girls(1)(2)(3)Young0.369*(0.195)0.342**(0.170)

0.343**(0.170)Hyperactivity Score at 2/3

0.417***(0.020)0.420***(0.029)Hyperactivity at 2/3 X Young-0.005(0.040)Boy0.934***(0.105)0.784***(0.100)

0.784***(0.100)N9579Table 6. Controlling for Pre-school Hyperactivity in Difference-in-Difference Estimates. Boys + Girls(1)(2)(3)Young0.430**(0.141)0.405**(0.133)0.404**(0.133)Hyperactivity Score at 2/3

0.410***(0.005)0.395***(0.025)Boy1.030***(0.075)0.894***(0.073)0.894***(0.072)Hyperactivity at 2/3 X Young0.028(0.041)3031Table 6b. Controlling for High Pre-school Hyperactivity in Difference-in-Difference Estimates. Boys + Girls(1)(2)Young0.430**(0.141)0.293*(0.148)Hyperactivity above 75th percentile at age 2/31.670***(0.135)Boy1.030***(0.075)0.946***(0.077)High Hyperactivity at 2/3 X Young0.444***(0.128)32Table 6c. Controlling for Pre-school Hyperactivity in Difference-in-Difference Estimates. Boys compared to Girls.BoysGirlsYoung0.483**(0.164)0.405**(0.133)Hyperactivity Score at 2/3

0.413***(0.027)0.375***(0.026)Hyperactivity at 2/3 X Young-0.016(0.069)0.076**(0.024)N97939508Conclusions33Children who are young relative to classmates exhibit more symptoms of hyperactivity, as assessed by parentsThis is true, even controlling for pre-school hyperactivityChildren with higher levels of pre-school hyperactivity (more likely to be boys), have a particularly difficult timePolicy?34Staggered school entry (twice per year?) and/or extra accommodation for relatively young children?More recess?Finland model (formal schooling starts at age 7)

Thanks!35Hyperactivity Score by Province36

Hyperactivity More Persistent for Boys than for Girls37

38Different Age Patterns for Boys and Girls. RD models. 6 month window.BoysGirlsYoung0.910***(0.217)0.522***Days from Cutoff0.0027**(0.0010)0.0006(0.0008)

39Different Age Patterns for Boys and Girls. DD models.BoysGirls(1)(2)(4)(5)Young0.521***(0.164)0.524***(0.164)0.433***(0.089)0.454***(0.090)Age in Months0.022(0.014)0.033(0.021)0.033(0.013)0.115***(0.020)Age Squared-0.0001(0.0001)-0.0007***(0.0001)