Book excerpt: Treetops is the Oxford Reading Tree series of fiction with built-in progression for pupils aged seven to 11. Specially written for children who need the support of carefully monitored language levels, this story, entitled Purple Buttons, seeks to be accessible, motivating and humorous. The series is organized into Oxford Reading Tree stages (from stage ten to stage 14), with each stage introducing more complex narrative forms, including: flashbacks and changes in viewpoint; descriptive writing; extended reading vocabulary; and more pages, more text, and fewer illustrations. Each stage is supported by the Teacher's Guide, which offers guidance on using Treetops to assess children's reading ability, and includes a variety of activities, many on photocopiable sheets.