Seamus served as Director of the National Foundation for Educational Research in England and Wales for 12 years until his retirement in 2005. He chairs the Education for All working group within the UNESCO UK National Commission and serves on the National Council for Special Education in Ireland where he chairs the Research and Communication working group. He has advised UNESCO and other international bodies on issues relating to assessment and special needs for over 20 years. He is founder editor of the European Journal of Special Needs Education, now in its 25th year, and edited Educational Research for 12 years. He has written or co-authored more than 20 books and numerous papers.

Seamus has evaluated and advised on research for universities and national authorities in many countries, with current or recent commitments in Chile, Italy, the Netherlands, Norway and South Africa. He sits on the Advisory Board for the Assessment and Teaching of 21st Century Skills project launched by Cisco, Intel and Microsoft and is an International Advisor for the International Step-by-Step Association supported by the Open Society Institute and the Soros Foundation. He holds visiting professorships at four universities and is currently a Marie Curie Senior Research Fellow at Trinity College Dublin.