Purpose: Assessment of agricultural advisory services is crucial to improve their quality and effectiveness. Farmer Field Schools (FFS) have been adapted to meet context specific needs in crop or farm management. This article investigates whether the diversity of FFS interventions is reflected in the assessment methods used to evaluate them. Design/Methodology/Approach: Through a systematic review of peer-reviewed literature we identified 180 articles and selected 34 that assessed FFS. Implementation was characterised based on farmers' participation and FFS topics. Assessment methods were analysed using a causal chain of inputs, outputs, outcomes, and impacts. Findings: Our results showed three types of FFS: (1) technology transfer; (2) consultative participation at cropping system level; and, (3) consultative or collaborative participation at farm level. Fifteen studies did not describe FFS implementation at all. Out of the 34 assessments, 23 focused on inputs (knowledge) and outputs (changes in practices, agricultural or economic performance) for farmers. Only six studies assessed long-term impacts of FFS. Theoretical implications: We found a paradox between the shift from a technology transfer to a participatory advisory services paradigm, and the implementation and assessment of FFS, which do not mirror this shift. Assessment methods remain based on assumed technology transfer, which is not suitable for the evaluation of participatory approaches and their results, including in terms of capacity to innovate. Practical implications: Assessing FFS as a collective and farmer-centered experiential learning approach requires appropriate evaluation methods that account for the diversity of contexts, FFS implementation, and the changes they generate. Originality/Value: The diversity of FFS has rarely been analysed to date. This article proposes a typology to go beyond FFS as a catch-all term and to guide their assessment.