This paper examines the impact of teachers' formative feedback on intermediate drafts on student writing development and its interrelationship with summative assessment. Formative feedback is advocated for its benefits on learners writing development; however, its usage in writing instruction at the upper-secondary level is met with frustrations from teachers and students alike. This paper endeavors to draw upon international research on the topic, synthesize the results and correlate it to the educational context of ESL teaching of writing in Swedish upper-secondary schools to elucidate what formative feedback practices are beneficial and how summative aspects can impact them. Research shows that feedback that is encouraging, investigative, and deals with global and local issues alike is more beneficial for facilitating writing development in a new genre. However, teachers should be mindful of overusing imperatives as they can act as demotivators, and they should also be mindful of the toll engaging with feedback takes on learners. Furthermore, teachers should not use grades to motivate feedback uptake, as it does not incentivize learners to do meaningful revisions. Lastly, more research should examine how formative feedback can illustrate students' writing standards without impeding benefits to writing development.