The purpose of a neuropsychological assessment is to describe a child's difficulties and strengths to enable treatments and contextual adjustments. Typically, the assessment is summarized in the form of a written clinical report. However, such texts have been criticized for being too difficult for parents and teachers to read and comprehend. The purpose of this pre-registered and randomized controlled study was to evaluate five writing rules to improve readability and accessibility in clinical reports: to structure the text with functional domains, exemplify cognitive tasks with examples from daily life, use examples from the daily life of the child, avoid jargon, and to write shorter sentences. We created two separate reports based on the same assessment information of a hypothetical child: one "standard" report, and one where the five writing rules were applied. One hundred teacher students at a teacher education program were randomized to read one of the reports, and then rated readability and answered a comprehension quiz. Results showed that the five writing rules led to improved ratings of readability, and helped readers recall more information immediately afterward. Effects were medium to large. Future studies need to investigate whether the findings generalize to parents and other potential readers. Additionally, future work should address how psychologists can be taught to improve their writing through writing guidelines. Clinical trial registration: https://aspredicted.org/ac96p.pdf.