(which frequently they do not) it should surprise no-one that laboratory provision does
not have a large impact on achievement measured through pencil and paper tests. These
often emphasise recall and the abstract application of principles. The reasons for
incorporating practical work in science have been thoroughly explored by Haddad and
Za'rour (1986) who argue its benefits whilst recognising the difficulty of measuring its
impact. The First IEA Science study noted positive effects of reported laboratory use in
three of the four developing countries in their sample but Heyneman and Loxley's 1983
study found no such effect. Lockheed, Fonancier and Bianchi (1989) did find positive
effects arising from teaching primary science in laboratories in the Philippines but note
that the magnitude of this was much less than the effect of frequent group work and of
frequent testing. The most recent IEA study (Postlethwaite and Wiley 1992) is complex
to interpret on the subject of practical work and achievement; it does suggest that where
students views of teaching indicate more practical work probably takes place, there is a
positive relationship with achievement in five out of nine cases. The weight of opinion
seems to lie with those who are sceptical about the measurable benefits of laboratory
science for achievement as conventionally measured, and who stress its high costs
(Wallberg 1991).
On the positive side, length of time spent on instruction is reported widely as having an
impact on achievement. Heyneman and Loxley (1983) note this in relation to general
science in India, Thailand and Iran. Fuller (1987) counts 12 out of 14 analyses
supporting this proposition. There are wide ranges between countries in the amount of
time allocated to teaching in different countries. Science instructional time varies by a
factor of more than two in the IEA Second International Science Study as does the
length of the school year. And actual variations will be greater still. In some countries
many of the official teaching days are not utilised for their intended purposes as a result
of teacher absenteeism, school functions, excessive examination practice, natural events
and casual holidays. The more time allocated to instruction the more is likely to be
learned, but there is no reason to suppose that the relationship is linear.
Feeding programmes are an established way of enhancing enrolment and increasing
retention. They are however often very expensive and may reduce teaching time if
teachers are involved in the preparation of food. School libraries also appear associated
with improved achievement, though there is very little data on patterns of use. Since
libraries tend to be found in better resourced schools with more favourable learning
conditions and better qualified staff it may be that the general association is not strongly
positive with library resources alone.
Pre-service teacher qualifications and training do show up in many studies as positively
related to achievement. The magnitudes of the effects are often moderate however. The
effects are difficult to measure - since children experience different teachers should
recent training be given the same weight as training ten years ago? - and the number of
years of schooling completed before training may be at least as important as the training