Minimum ratio of school psychologists needed as mental illness soars We’re sorry, this service is currently unavailable. Please try again later. Dismiss Normal text size Advertisement Mental health experts and principals are pushing for a new national benchmark of one school-based psychologist for every 500 students across Australia to address the alarming rates of mental illness among children. About 600,000 school-aged children - about one in seven - experience a mental health disorder each year with 20 per cent of those starting primary school education showing high levels of emotional problems. Mental health experts want a new national benchmark of one school-based psychologist for every 500 students.