Aspiring headteachers will have to submit a portfolio of evidence and face an in-depth grilling from an expert panel to prove their capabilities as part of a new approach to developing school leaders.
The revised arrangements for the National Professional Qualification for Headship (NPQH) have been revealed by the Assembly government following a wide-ranging review of professional standards.
Although the NPQH has been a statutory requirement for headship in Wales since 2005, school inspectorate Estyn recently said it was "outdated", "ineffective" and failing to produce enough heads.
Around 150 candidates complete the NPQH ever year, but on average only 70 to 80 new heads are needed. Some 700 people in Wales currently hold the qualification but do not work as headteachers.
The Assembly government said a "more rigorous" approach to developing school leaders, linked to the school effectiveness framework, was needed to produce the best candidates for headship.
The new NPQH, which will start in September, will be focused on a portfolio-based assessment against new leadership standards, with coaching and mentoring support available for candidates.
Evidence gathered in the portfolio will be examined in detail by an independent expert panel, and candidates will then face an in-depth interview to scrutinise whether their leadership practice meets the standards. Guidance to support the new approach is currently being developed and will be made available online in the summer term.
The new approach has been welcomed by headteachers' representatives. NAHT Cymru director Anna Brychan said: "We're pleased that progress is being made on this. We have members who have been frustrated that the brakes have been put on their careers because they weren't able to access NPQH.
"Schools are finding it hard to recruit heads. Those enthusiastic, able middle leaders who want to take up headships are like gold. We have to offer them the best training."
ASCL Cymru secretary Gareth Jones said: "This is a positive step forward; a qualification rooted in experience rather than a taught modular programme. The mentoring support is essential, and we expect mentors to be picked from the very best. The NPQH was criticised for lacking in staff management issues, and this is where the mentors will come into their own."
The General Teaching Council for Wales has also welcomed the revision, which reflects many of its own proposals outlined in a recent position paper on school leadership.
Its chief executive, Gary Brace, said: "We are very pleased that there is such a correspondence between our position paper and the new approach . We are particularly pleased they have recognised the vital need for coaching and mentoring, and we also hope that candidates will get to experience a range of different leadership styles."
A small group of candidates has already been selected for a pilot scheme that will run until October.
In its letter to stakeholders, the government said: "The primary purpose of this pilot will be to focus on the assessment panel approach to ensure it provides sufficient challenge and rigour so that only those candidates who have demonstrated that they are ready for headship are awarded the NPQH."