Douglas Osler said HMI's latest report showed that "the vast majority of drama teachers have responded positively to national developments". Attainment levels were good.
Although the past 15 years have been a period of rapid expansion, fewer than half of secondary schools offer drama courses from S1 to S4 and only a third for pupils in S5 and S6.
In a statement accompanying the report, Mr Osler gave drama a more defined place in the curricular sun than ever before, making it clear its importance to the development of creative skills which were "vital for the future prosperity of Scotland".
But inspectors found that while most departments had good facilities for teaching drama, "the further development of the subject requires improvements in staffing, accommodation and resources".
The report, the 16th in HMI's series on effective learning and teaching in secondary schools, urges authorities and heads to step up the provision for drama, including "secure and accessible storage which adheres strictly to health and safety guidelines". There should also be a range of good quality audio-visual resources, props and texts, the report says. Teachers should have the chance to undertake staff development to ensure they are up to speed with the course changes resulting from Higher Still.
HMI also urges drama teachers to ensure that pupils "create drama out of relationships and interactions which are not always confrontational or spectacularly dramatic". This approach would "counteract a tendency to explore cliched themes and develop a more subtle awareness of dramatic interrelationships".