High-stakes assessments prominently influence what is done in secondary school science lessons ('washback' effects). It is therefore important that assessments of knowledge and understanding gained from practical work are constructed to reward and incentivise effective practices in practical work. To do that, they must differentiate between pupils who have experienced practical work in different ways. This empirical, mixed-methods study identifies generalizable characteristics of written assessments that differentially reward pupils who experienced practical activities through hands-on work, teacher demonstration, video demonstration, or reading about the activity. Conclusions are drawn from 1486 post-intervention tests completed by pupils aged 14-15 in England, from lesson observations and teacher interviews. This study also identifies pedagogical practices that were more noticeable in practical work that was most rewarded by the written assessments: the work was teacher-guided; and pupils were encouraged to be active participants. Existing literature describes negative washback effects of high-stakes, written assessments that limit the use and effectiveness of practical work as a pedagogical tool. We describe ways in which written assessments could be constructed to better reward effective practices in practical work (practices that better support learning), with the intention of having positive washback effects on pedagogy by better incentivising these practices.