The figures emerged as the Assembly government is considering a national action plan to clarify the role of school nurses in Wales.
The latest figures available, from the end of 2004, show there were 249 school nurses employed by NHS trusts and local education authorities in Wales -approximately one for every seven primary and secondary schools.
Many work part-time and just two are aged under 30. A fifth are due to retire by 2014.
The number of school nurses across Wales varies considerably: most (17 per cent) are employed in Gwent, with just 3 per cent in Ceredigion.
Jane Davidson, minister for education, lifelong learning and skills, revealed the figures in response to the children's commissioner's annual report.
According to Assembly government figures, places on centrally-funded school nursing training courses in Wales have doubled annually since 1999 from 12 to 24. But they still fall well short of Royal College of Nursing targets set last year for a nurse in every school by 2010. Liz Allan, chair of the RCN's school nurse forum, said the days of nit-nursing were gone.
"The modern school nurse might attend a child-protection conference one day, deal with a broken leg on another, and provide advice on nutrition, exercise, drug or alcohol abuse the next," she said.
In his annual report, children's commissioner Peter Clarke called for more school nurses to tackle obesity, sexually transmitted diseases, teenage pregnancy, drugs, smoking and alcohol.
He said more nurses needed to become involved in innovations in schools - such as healthy eating schemes and personal and social education programmes.
In response, Ms Davidson announced a sub-committee was exploring the role of the school nurse. She said a major problem was the "patchy" service provided across NHS trusts and LEAs. The sub-committee has already recommended an intensive recruitment programme, and agreeing in writing the new remit of a school nurse.
Ms Davidson said: "It is right that there should be increasing recognition at a national policy level of the importance of school nursing - and the need for the development of a modern school nursing service."
An RCN report last year claimed school nurses throughout the UK are over-stretched and under-resourced. In a survey, nine out of 10 nurses said they had neither the time nor resources to provide the full range of services pupils needed.