A growing policy emphasis on measurement and outcomes has led to cultures of performativity, which are transforming what educators do and how they feel about themselves in relation to their work. While most analysis of performativity in education has focused on schools, this article investigates parallel developments in youth work. Youth work is a practice of informal education, in which young people learn and develop through activities, conversation and association. Its evaluation and monitoring have changed over the past two decades, as funding has become tied to targets and measureable outcomes. This article focuses on the English context, where government and third sector organisations are promoting a "youth impact agenda", encouraging organisations to predefine and measure their outcomes. Drawing on data from interviews and focus groups with youth workers, the article argues that the current emphasis on impact risks further marginalising youth work at a time when this practice is already suffering from extensive spending cuts. The article concludes that we need to re-think the purposes and processes of evaluation and accountability - in youth work and beyond--in ways that genuinely value the perspectives of young people and grassroots practitioners.