As a minimum, all evaluation projects must ensure that they are fully in line with the ethical research policies and requirements of all institutions which they will investigate or in which they are based.
A wide variety of documents are available to advise on ethical research and ethical investigation. Particular care needs to be taken when systems or products being tested could have effects on people's health or performance. In education, for example, it is not acceptable to offer a service to one group and deny it to another, just to create a 'controlled' experiment.
As examples of ethics statements, see the ESRC's Research Ethics and Confidentiality page and the EPSRC's Guide to Good Practice in Scientific and Engineering Research.