I returned to the Netherlands as a professor of experimental physics at Radboud University Nijmegen in 1998. After having enjoyed more than 10 years almost exclusively doing research work at CERN and elsewhere, I found (as I had strongly suspected) that I very much enjoyed teaching. Teaching first-year undergraduate physics courses, I came into contact with high-school teachers who were assisting students with the transition between secondary school and university. While successful for a broad group of students, many realised during their first year of university that studying physics was rather different from what they had imagined when they were still in school. As a result, there was a significant drop-out rate.

An opportunity to remedy this situation came when I read about a cosmic-ray high-school project in Canada led by experimental particle-physicist Jim Pinfold. Soon thereafter, and independently, a Nijmegen colleague, Charles Timmermans, came to me with a similar proposal for our university, and in 2000 we initiated the Nijmegen Area High School Array. Two years later, together with others, we launched the Dutch national High-School Project on Astrophysics Research with Cosmics (HiSPARC), which involved placing scintillator detectors on the roofs of high schools to form detector arrays. This is an excellent mixture of real science and educating high-school pupils in research methods. It has been a lot of fun to build the detectors with pupils, to legally walk on school roofs, and to analyse the data that arrive. Of course reality is unruly and it is sometimes hard to keep the objectives in focus: the schools can tend to be rather casual, if not careless, about the proper function of their set-up, whereas for the physics harvest it is essential to have a reliable network.

HiSPARC had an interesting side effect. While working with my group on the DΦ experiment at the Tevatron, focusing on finding the Higgs boson, I was, more or less adiabatically, pulled towards the Pierre Auger Observatory (PAO)   the international cosmic-ray observatory in Argentina. The highest-energy particles in the universe are very mysterious: we don’t yet know precisely where they come from, although the latest PAO results suggest we’re getting close Extreme cosmic rays reveal clues to origin. Nor do we know how they are accelerated to energies up to 100 million TeV. My involvement as a university scientist in a high-school project has completely redirected my research career, and for the past five years I have spent all of my research time on the PAO.

Prompted by my teacher network, around 10 years ago I organised a joint effort between six nearby high schools concerning a new exam subject introduced by the Dutch ministry – “nature, life and technology”, which integrates science, technology, engineering and maths (STEM) subjects. Every Friday afternoon, 350 pupils come to our faculty of science, which itself is an organisational and logistical challenge. The groups are organised during the course of the afternoon depending on the activity: a lecture for all, tutorials, and labs in biology, chemistry, physics, computer science and other subjects. Around 10 different locations in the building (and sometimes outside) are involved, and for every 20 25 pupils there is one teacher available. Following this project, in 2011 I initiated a two-year-long pre-university programme for gifted fifth and sixth graders in high school, which also takes place at the university and involves about 20 teachers and 14 university faculty members. The first cohort of pupils arrived in 2013, and one of the first graduates in the programme recently completed an internship at CERN.

Admittedly it is a lot of work. But it has been worth the effort. By thinking about how to teach particle physics to pupils with different backgrounds and experiences, I have gained more insight into the fundamentals of particle physics. Even the sometimes tedious experience of bringing school managements together and getting them to carry out projects outside of their comfort zones has prepared me well for some aspects of my present duty as president of CERN Council. Working with pupils and teachers has enriched my life, without having to compromise on research or management duties. And if I can combine such things with a research career, there seems little excuse for most scientists not to help educate and inspire the next generation.