crime in schools,
Smallest Geographic Unit:
Date of Collection:
Unit of Observation:
Public elementary and secondary schools in the United States.
Data Collection Notes:
Users interested in obtaining a restricted-use data file containing more detailed information can file an application for the data with the Institute of Education Sciences/National Center for Education Statistics (IES/NCES), Restricted-data Licenses.
The SSOCS is the primary source of school-level data on crime and safety for the United States Department of
Education. It provides nationwide estimates of crime, discipline, disorder, programs, and policies in public
schools. Data on crime, violence, and disorder in the nation's schools are collected to provide policymakers,
parents, and educators with the information necessary to identify emerging problems and to gauge the
safety of American schools.
SSOCS:2004 was conducted as a mail survey with telephone follow-up. Six months before the
onset of data collection, NCES began working with the school districts of sample schools that
required prior approval to participate in the survey. In late February 2004, advance letters were
sent to school administrators of sample schools that included the date of the first questionnaire
mailing and a toll-free number to call with any questions. Approximately one week later, SSOCS
questionnaires were mailed to administrators with a cover letter describing the importance of the
survey and a brochure providing additional information about it.
On the same day the questionnaires were mailed to schools, letters were sent to sample district
superintendents and the Chief State School Officer of each state to inform them that schools
within their districts and states, respectively, had been selected to participate in SSOCS:2004.
The letters included information about the survey and were accompanied by a copy of the
questionnaire and brochure that were sent to schools. The letter was not designed to ask for
permission from these officials to participate in the survey but rather, it was designed by NCES as a
vehicle to enhance participation.
Starting approximately one week after the first questionnaire mailing, follow-up telephone
prompts were used to verify that the questionnaire was received and to encourage survey
response. As an alternative to replying by mail, data were also accepted by fax submission and
over the telephone. Data collection ended on June 4, 2004. Returned questionnaires were
examined for quality and completeness using both manual and computerized edits. Out of 227
items on the questionnaire, 101 were identified as key (critical) items. If the survey had more
than 40 percent of all items missing or more than 20 percent of critical items missing, the
respondent was recontacted to resolve issues related to the missing data. In cases where the
recontacts failed to produce a satisfactory resolution, imputation was used to resolve data quality
issues for questionnaires that had at least 60 percent of all items and 80 percent of critical items
completed. Schools whose questionnaires did not meet the 60/80 criterion and for which
recontact was not successful were reclassified as nonrespondents.
The sampling frame for SSOCS:2004 was constructed from the public school universe file created for the 2003-2004 Schools and Staffing Survey (SASS). The SASS frame was derived
from the 2001-2002 NCES Common Core of Data (CCD) Public School Universe file. The CCD is an annual national database of all public K-12 schools and school districts. Certain types of schools are excluded from the CCD Public School Universe File in order to meet the sampling needs of SASS, including those in the outlying United States territories, overseas Department of Defense schools, newly closed schools, home schools, and schools with high grades of kindergarten or
lower. Additional schools are then excluded from the SASS frame to meet the sampling needs of SSOCS, including local education agencies that appear to be schools and "intermediate units" in California and Pennsylvania.
Further information on sampling can be found in the School Survey on Crime and Safety: 2003-2004 Data File User's Manual.
Sample weights allow inferences to be made about the population from which the sample units
were drawn. Because of the complex nature of the SSOCS:2004 sample design, these weights are
necessary to obtain population-based estimates, to minimize bias arising from differences
between responding and nonresponding schools, and to calibrate the data to known population
characteristics in a way that reduces sampling error. The procedures used to create the SSOCS
sampling weights are described below. An initial (base) weight was first determined within each stratum by calculating the ratio of the
number of schools available in the sampling frame to the number of schools selected. Because
some schools refused to participate, the responding schools did not necessarily constitute a
random sample from the schools in the stratum. In order to reduce the potential of bias from
nonresponse, weighting classes were determined by using a statistical algorithm similar to
CHAID (i.e., chi-square automatic interaction detector) to partition the sample such that schools
within a weighting class were homogenous with respect to their probability of responding. The
predictor variables for the analysis were instructional level, region, enrollment size, percent
minority, student-to-teacher ratio, percentage of students eligible for free or reduced-price lunch,
and number of full-time-equivalent teachers. When the number of responding schools in a class
was sufficiently small, the weighting class was combined with another to avoid the possibility of
large weights. After combining the necessary classes, the base weights were adjusted by dividing
the base weight by the response rate in each class, so that the weighted distribution of the
responding schools resembled the initial distribution of the total sample.
The non-response-adjusted weights were then poststratified to calibrate the sample to known
population totals. For SSOCS:2004, two dimension margins were set up for the poststratification:
(1) instructional level and school enrollment size, and (2) instructional level and locale. An
iterative process known as the raking ratio adjustment brought the weights into agreement with
the known control totals. Poststratification works well when the population not covered by the
survey is similar to the covered population within each poststratum. Thus, to be effective, the
variables that define the poststrata must be correlated with the variables of interest, they must be
well measured in the survey, and control totals must be available for the population as a whole.
Similar to SSOCS:2000 (ICPSR 3964), all three requirements were satisfied by the aforementioned
Mode of Data Collection:
Unweighted response rate: 74.7 percent,
Weighted response rate: 77.2 percent
Extent of Processing: ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of
disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major
statistical software formats as well as standard codebooks to accompany the data. In addition to
these procedures, ICPSR performed the following processing steps for this data collection:
Standardized missing values.
Checked for undocumented or out-of-range codes.