The exit interview is a great idea. Numerically with more people leaving that staying, if you can halve the rate of people leaving, as opposed to focussing on doubling the rate of people coming in the door...its likely to be a more successful strategy. Its kinda tough though to get the real reason people might be leaving sometimes though...e.g. people will rarely say 'your aikido sucks' but come up with something else instead.
Whatever the strategy I think the important basics have to be there such as
- a critical mass of students (maybe around 8 or so), fewer than than and the person leading the practice has to expend all the energy into creating life in the dojo
- practice twice a week seems to be the norm, usually with a gap between the days and avoiding fridays
- pictures of people enjoying them selves seems to manage expectation
- a teacher with a skill base perhaps some charisma and nothing too off putting
FWIW i looked at your website, and perhaps advertising short 'social contracts' (through requirement to enrole in a community college) may bring people in quite successfully, but can also create the expectation that because it will finish in xxx weeks then many have an implied permission/expectation (probably not the right word ) to move on and try something else afterwards rather than stay on ...least ways we found this with beginners courses