Ask a school owner why teachers leave and the answer is almost always salary. Ask the teachers and it usually is not.
In conversations across member schools, the reasons that come up first are timetable instability, no path to seniority, and being asked to do administrative work with no notice. All three are cheaper to fix than a pay rise.
What tends to work
Publish the timetable a term ahead. A teacher who cannot plan their week cannot plan their life. This costs nothing and is consistently the single most valued change.
Create a named senior teacher role. Not necessarily paid more at first — but named, with a defined remit. People stay where they can see a next step.
Separate teaching from administration. If a teacher is covering the front desk during a free period, that is not a free period.
Give two weeks' notice of any cover. Emergencies happen; systematic last-minute cover is a scheduling failure being paid for in goodwill.
Exit-interview everyone, and write it down. Most schools have no record of why staff left, which means the same cause repeats for years.
None of this replaces paying people properly. But schools that have done these five things report markedly longer tenures at the same salary.