bility and validity.
Schools, parents, and participants provided informed consent prior
to any testing. A qualified educational psychologist assessed each
student individually in a quiet room at school over 3 days. The first
session involved a familiarization with the assessor and a discussion
about the longitudinal study. Participants were allowed to terminate the
session or opt out of a test if they wished. All tests were administered
using the standard procedures in the manuals. Participants received a
certificate of merit for participation in the study.
For the writing measure (WOLD; Wechsler, 1996), assessors noted the
time taken to produce the written text in seconds and participants were
asked to read back their written texts to prevent penalizing children
who were poor spellers; Unclear words were noted on a separate sheet.
Two research assistants performed reliability checks for the six
dimensions of the analytical scoring of the WOLD. In the case of an
interrater disagreement, the scores were further discussed with the
research team and informed the final scoring of the texts. Mean
interrater reliability for a randomly selected 36 ratings was 80% with a
Kappa score of .66. The research assistants counted spelling errors and
the total number of words produced, excluding numerals. There was 100%
agreement between raters for these measures.
We report data only for children completing the writing measure at
age 16 (N = 58). To normalize performance on the test we transformed
each standard score, the centile or T score, to a z score to provide a
common metric for analysis. In this section, we first examine student
performance in written text production, both on the total analytic score
of the WOLD (Wechsler, 1996) and in terms of words written and errors
produced. We then describe the relationships between language and
literacy and the total analytic score on the WOLD. To consider further
the different relationships between the variables, we present two path
analysis models to examine the magnitude and significance of the
relationships between literacy, language, and written text production
concurrently and over time.
STUDENT PERFORMANCE IN WRITTEN LANGUAGE AT 16
As a group, the participants performed poorly on the total analytic
scale of the WOLD (Wechsler, 1996) with a mean z score of -2.20 (SD =
1.14); this pattern of performance did not vary by gender (girls M =
-2.34, SD = .89; boys M = -2.15, SD = 1.21; t = 0.58, df = 56, ns) or
special and mainstream settings (mainstream M = -2.00, SD = 1.21;
special M = -2.50, SD = .98; t = 1.6 df = 56, ns). As such, all further
analyses treat the participants as one group.
Performance on the written language measure was significantly
poorer than the students' nonverbal ability scores (t = 9.12, df =
56, p < .0005, Cohen's d = 1.31). We examined the extent to
which performance in writing was commensurate with language and literacy
assessments through a series of repeated measures ANOVAs. Performance on
the written language measure was poorer than performance on the oral
language measures, F(3, 168) = 51.89,p < .0005, [eta][p.sup.2] = .48.
Post hoc comparisons, adjusting for multiple comparisons, indicated that
performance on the written language measure was significantly poorer
than both vocabulary and listening to paragraphs (p < .0005), but did
not differ significantly from the expressive language measure, recalling
sentences. We also considered the literacy measures of spelling, reading
decoding, and reading comprehension in relation to writing. There was a
significant effect of literacy measure, F(3, 159) = 8.336, p < .0005,
[eta][p.sup.2] = .14. Post hoc comparisons adjusting for multiple
comparisons indicated that performance on the written language measure
was significantly poorer than spelling (p = .001), reading decoding (p =
.005), and reading comprehension (p < .0005). Participants thus
experienced significant difficulties in the production of written text;
the degree of impairment for writing, as measured by norm-referenced
tests, was significantly greater than t