ST, SH/HOD are identified and groomed by school management..

For ST, you must be very strong with your T&L and demonstrate strong curriculum leadership. It focuses on teaching and mentoring.

For GEO 5 teachers not on leadership track, only 1 out of 10 will eventually become ST. Your school must support you, endorse your for panel interview. Too be honest, ST ship is not glamorous, except you will eventually hit SEO 1 grade similar to SH. If you are in it for the money, supplementary external private tuition would have covered way more than SEO 1.

If you are good, the school would have identified you and groomed you. No need to chase after it. Too be honest, I would rather do what's required of a Happy Ordinary Teacher at GEO 5.