Schools should make more time for creative subjects such as art and music, which are being "squeezed out" of the curriculum, headteachers will hear this weekend.
Welsh head Chris Howard, who will be invested as president of the National Association of Head Teachers at its annual conference in Brighton tomorrow, will use his inaugural speech to highlight his concerns over the "narrowing" of the school curriculum and the "negative" focus on test results and league tables - particularly in England.
Dr Howard, head of Lewis School Pengam in Gilfach, near Caerphilly, will tell heads from across the UK that they should try to engage pupils' more creativity.
"Many schools are concentrating on the STEM (science, technology, engineering and maths) subjects at the expense of the creative arts," he told TES Cymru.
"In many schools, music in particular is being given pretty short shrift."
To demonstrate the benefits of music tuition, Dr Howard has invited the Caerphilly Youth Band to open the conference.
The theme of the conference is "Making our horizons sing" - the signature words on the facade of Cardiff Bay's Millennium Centre.
Dr Howard will say that the talent of individuals must be fostered in schools.
"We need to show that education is more than just a narrow set of test results, which currently seems to be the case in England," he said.
"Schools are constantly being evaluated on what they produce on literacy and numeracy scores, but that's only part of what children go to school to learn and achieve."
Dr Howard will also hit out at the growing amount of paperwork that school leaders are expected to deal with.
"Too many heads, particularly in the primary sector, are spending too much time on bureaucratic stuff and not enough time in the classroom. It's getting people down," he said.
Dr Howard's presidency of the heads' union is the culmination of a 31-year career in secondary schools in Wales and England, including 15 years as head of Lewis School.