Good teachers, who over time and on the basis of their seniority and relative merit become principals, train themselves on the job without the possible advantage of structured learning or preparation.
The challenges of a subject tutor, however competent and committed, are vastly different than those of school leaders/principals. While some do respond very positively and learn the job as they grapple with leadership challenges, some do not. This trial & error, given short time window in the context of competitive knowledge societies, may not be the best available option. Given the demographic advantage of a young society, we face an immediate challenge of educating and training them right or else, this advantage could well rebound as a colossal liability. It is action time NOW.
India does not boast of any credible program that prepares educational leaders for today's and tomorrow's schools. Some peripheral, very short and somewhat irrelevant programs may be available. Global experience in preparation of school principals suggests that online and part-time programs have very limited impact, if at all. Experience sharing and peer learning goes completely missing. Mere certification does not create educational leaders.