Having trainee frees up some teacher time - they can get marking/planning done while supervising
Mentoring trainee teachers requires additional training, lots of extra meetings 1-1 with the trainee and plenty of paperwork/red tape. Detailed lesson observation forms are required to be completed regularly as part of the trainee´s evidence towards their QTS. Regular meetings with trainees also have to have completed sheets for their files.
If a more senior teacher is involved in training they are taking on board extra work and not less. Mentors don´t get any extra pay for this unless they are leading mentoring within the school. Training schools get additional funding but I am not aware of additional payments to other schools per trainee they take on.
Are our schools attractive enough so that out Richmond Schools will have the vacancies filled for September?
I hope so. One way of recruiting and retaining high calibre maths teachers and other shortage subjects is to offer some extra incentives. It is not unusual in schools for the Assistant Heads/Deputies to be teachers of shortage subjects.