Sports provision in schools is fragile and inadequate, resulting in poor levels of fitness among pupils, according to the national body for rugby.
Scottish Rugby said its programme to increase opportunities for pupils to play the sport had highlighted "some serious problems" within schools' PE and sports provision.
In a written submission to Holyrood's Sport Committee, the organisation said "the fragile nature of sports provision which is so often dependent on PE staff on short-term contracts" can make it difficult to sustain, and impossible to increase, participation in rugby in schools.
It said many schools were wholly dependent on non-PE staff who volunteer their time to support their sport while there was also insufficient provision of sport and physical activity within the PE curriculum, such as opt-outs and inactive time.
Scottish Rugby said it had also found that some pupils possessed "very poor levels of physical fitness, physical competence or generic sporting skills/experience as a result of inadequate PE provision in primary and secondary schools", and some PE teachers lack "either the physical competence to teach sports, or lacking the skills, experience or qualifications to confidently teach technical elements of sports".
The organisation is to appear alongside other governing bodies to give evidence in the Committee's inquiry into support for community sport.
Scottish Rugby's written submission calls for action from the Scottish Government and the education profession.
It says: "Schools need to be supported and financed to ensure that there is adequate rugby training and we would like to see all local authorities developing robust sports plans both for their schools and communities, which recognises the importance of rugby as a route to a healthier lifestyle.
"We urgently need action from government, the education profession, teacher-training institutions, local authorities and sporting agencies to ensure these opportunities and benefits are delivered in all schools nationally.
"Scottish Rugby believes that the Scottish Government must ensure that there is a lasting legacy from the Olympic and Commonwealth Games. In order to achieve that, there must be sustained investment in Scottish rugby at all levels."