As shown in table 4, once we account for the endogeneity of moves, a very different picture of mobility emerges. Structural moves continue to have a significant negative impact on performance in the years after the move, decreasing performance by 0.096–0.113 in ELA and 0.182–0.200 in math, depending on the parameterization of the grade span instruments. This is similar to but slightly larger than the results with student fixed effects alone. In contrast to the fixed effects results, however, IV results show nonstructural moves have no significant medium-term impact in either ELA or math. Thus, it seems that estimates of the impact of nonstructural mobility from the student fixed effects models may be biased due to the endogeneity of nonstructural mobility. In particular, the compliers who are contributing to the estimated effect in the IV model are likely to be making more “strategic” moves based on the cost–benefit logic described previously, such that OLS estimates did not accurately capture the impact of nonstructural mobility for this group.
| ELA | Math | |||
|---|---|---|---|---|
| (1) | (2) | (3) | (4) | |
| Post-summer move | ||||
| Structural | −0.113*** | −0.096*** | −0.200*** | −0.182*** |
| (0.017) | (0.014) | (0.023) | (0.019) | |
| Nonstructural | 0.020 | 0.043 | 0.089 | −0.025 |
| (0.091) | (0.069) | (0.125) | (0.089) | |
| Instruments | ||||
| Building sale | Y | Y | Y | Y |
| Terminal and entry grade | ||||
| Quadratic | Y | N | Y | N |
| Nonparametric | N | Y | N | Y |
| Observations | 342,685 | 342,685 | 343,832 | 343,832 |
| Unique students | 88,241 | 88,241 | 88,254 | 88,254 |
| ELA | Math | |||
|---|---|---|---|---|
| (1) | (2) | (3) | (4) | |
| Post-summer move | ||||
| Structural | −0.113*** | −0.096*** | −0.200*** | −0.182*** |
| (0.017) | (0.014) | (0.023) | (0.019) | |
| Nonstructural | 0.020 | 0.043 | 0.089 | −0.025 |
| (0.091) | (0.069) | (0.125) | (0.089) | |
| Instruments | ||||
| Building sale | Y | Y | Y | Y |
| Terminal and entry grade | ||||
| Quadratic | Y | N | Y | N |
| Nonparametric | N | Y | N | Y |
| Observations | 342,685 | 342,685 | 343,832 | 343,832 |
| Unique students | 88,241 | 88,241 | 88,254 | 88,254 |
Notes: Robust standard errors, clustered by first-grade school and middle school by cohort, in parentheses. Post-summer move is equal to 1 in all years after a student moves schools between June and October. Summer moves made after the completion of a terminal grade are structural moves and summer moves made after the completion of a nonterminal grade are nonstructural moves. All models include controls for poverty, English proficiency, home language, participation in special education services, mid-year moves, building type, residence borough, grade, and year. Models in columns (1) and (3) use the number of years between a student's grade in t and the completion of the terminal grade of his first-grade school (YearsPre) and this number squared, the number of years between the beginning of a student's grade in year t and the completion of the grade after the terminal grade of a student's first-grade school (YearsPost), and an indicator equal to one in the summer following the completion of the terminal grade of a student's first-grade school (Terminal) as grade span instruments. These models also include the number of years between a student's grade in t and the entry grade of his closest ZIP code (YearsPreMS) and this number squared, the number of years between a student's current grade and when he would have entered the lowest grade of his middle school (YearsPostMS), and an indicator equal to one in the summer before a student would enter the closest middle school if he started on time (Entry). Models in columns (2) and (4) use a vector of indicators that are the interaction between a student's current grade and the terminal grade of his first-grade school (
gT) and a vector of indicators that are the interaction between a student's current grade and the entry grade of his closest middle school (ηgE). All models use the interaction between an indicator of whether a student's current building of residence was sold between t − 2 and t − 1 and an indicator for the building type as instruments for school moves.
***p < 0.01.