KS3: Discuss human rights and responsibilities (1a CE PoS at KS3), public services and "opportunities to contribute" (1c), the work of community-based voluntary groups (1f), as well as moral, social and cultural issues (2a). World Blood Donor Day on June 14 is a natural focus here for assemblies, class, or year-group activities. (Note that blood donors must be fit and healthy, aged 17 to 60, and weigh at least 50kg - 7st 12lb)
KS4: Teachers could explore the need for blood donation, the reasons for giving blood (altruism), variance in global blood supply and demand (inequality), social responsibility (who should donate?), ethical dilemmas (Jehovah's Witnesses and operations), or use case studies of lives saved by blood transfusions.
One area for enquiry might be "Should blood donation be made compulsory by law?" where tensions between individual freedom of choice and social responsibility can be investigated. As a first step, go to www.blood.co.uk, or try the brief list of "interesting blood facts" at www.heart-transplant.co. uk