Prefer Level 2 more than level 1. In HK, every Lv 1 can enroll lv 2 after a year, but having lv 2 depending on their abilities.
Lv 1 -copy from itf
3. PLAYING LEVEL
3.1. Ability to rally with at least one competent stroke with the student to enable a practice.
3.2. Ability to demonstrate all of the basic techniques from an easy feed.
3.3. Ability to feed as appropriate to the situation.
Lv 2 - copy from
http://www.itftennis.com/shared/medialibrary/pdf/original/IO_25023_original.PDF
3. PLAYING LEVEL
3.1 Experienced tournament player at least at national level.
3.2 Ability to be a sparring partner with tournament players.
3.3 Ability to demonstrate all of the advanced techniques.
3.4 Ability to feed as appropriate to the situation.