itself. One recent study (Lockheed et al 1986) suggests that other inputs i.e. textbooks
can be substituted for additional training since textbook use and training did not interact
in their data and the effects of textbooks were greater. Very little evidence exists on the
effectiveness of in-service training. Those studies that do exist are generally positive
but often have no means of controlling for the effects of training as opposed to the traits
of the teachers who choose to take advantage of it. Those involved are generally the
more motivated and skilled in the first place. Of course it is also likely to matter what
teachers are being trained to do and what kind of students they are teaching though this
also is also largely unresearched.
There is little doubt on the margin that textbooks do have a major impact on
achievement in most subjects, and probably the more so in science and other subjects
which depend on special school based resources. Unfortunately beyond the level of the
existence of textbooks in reasonable quantities there is little research to indicate at what
point additional written material ceases to have an effect (the Philippines study
mentioned above is an exception); or what the relative impact of different types of
material is teachers' guides, student texts, worksheets, reference books. And every
teacher has opinions, often well founded, about good and "bad" Every textbook is not
the same - some have inappropriate reading levels, some are poorly structured, some
contain factual errors, some are produced with poor quality and uninteresting design
and contain heavy gender stereotyping.
2.2.2 Recent methodological developments
Ridell (1989) has recently offered a critique of the school achievement studies
literature. This argues that the first wave of studies in the 1960s in developed countries
made considerable use of production function like models used by economists in
specifying variables. The second wave, placed more emphasis on process variables -
e.g. teaching styles - and the educational rather than statistical significance of findings.
A third wave is now developing which uses multi-level modelling techniques that can
accommodate the self evidently hierarchical nature of data on school systems (students
learn in classes which are part of schools which are part of districts and national
systems). Most school achievement studies in developing countries, she argues, have
been undertaken using the methods of the first wave. These have limitations, not least a
hazardous reliance on a particular statistical procedure to define the proportion of
variance associated with different variables which leaves much variance explained, and
is unable to account adequately for variance arising from different levels or, for
example, for the effects of selection. As a result it may be that the differences attributed
to school rather than individual and home background factors may have been
exaggerated when comparisons are mad between developed and developing countries.
Heyneman (1989) defends the use of the analytical techniques of the 1970s
(predominantly ordinary least squares) since multi-level modelling was not available at