Since your essay isn't specifically about SEN but being an inclusive practitioner, you can certainly use materials gained at your prep school as a basis for your argument. See how a teacher takes into account (differentiates) varying ability (no matter how slight) and learning styles. Use of extension tasks for the more able and support materials for the less able. Gender differentiation and cultural diversity (if any). How it is reflected in planning, in groupings, seating plans. Use of support staff. Technological help, such as computer programmes, AV, IWB. Assessment methods. You can certainly trace your development by comparing your plans from previous years, in your feedbacks (crits), and pupil attainment. You'll find a lot of articles and research findings on inclusion, such as in Pollard's Reflective Teaching.