This paper explores the sample design effects that have been observed in recent large scale educational surveys conducted in Australia, including international surveys such as PIRLS, TIMSS and PISA, as well as surveys conducted under Australia’s National Assessment Plan, including surveys in Civics and Citizenship and ICT Literacy. Design effects will be examined both nationally and also by subpopulation, for example by location. Comparisons will also be made with design effects observed in other countries. The paper will explore the factors underlying the observed design effects - for example the degree of segregation of the Australian schooling system, the availability of stratification variables, and the desire to present outcomes across a number of levels and reporting groups. Implications with respect to the precision of outcomes estimated from the survey - the size of standard errors and confidence intervals – will form part of the discussion.