The results of studies may not be applicable or transferable if the participants in studies are very different from those of interest to you.
Systematic reviews of studies that only include a selected minority of schools, teachers or learners may not provide results that are relevant to most schools.
For example, a reading intervention may have worked very well with primary school students in Canada but that does not automatically mean that it will work well with your students in the UK.
BEWARE of adopting a promising intervention without comparing the context of the study to your own.
REMEMBER that results of systematic reviews of studies in highly selected groups of people may be misleading.