This paper analyses the combined effect of school entry-age increase and the changes in preschool provision on educational achievement using a difference-in-difference specification. Achievement is assessed using the score on national standardised tests across a range of subjects. The analysis uses the changes in policy in different years across two states in Australia. I find positive effects for several subjects across different grades. Results are robust to falsification tests. In one state, however, cohorts starting school during the policy transition period are adversely affected, possibly due to disruption in preschool education. (author abstract)