In reply to melocoton:
Very limited sample, however the two people I know (both SMT), only hung around due to retirement and job movement being limited(Age/salary) both worked vast hours far above what they had. They didn't speak badly of it, but nor were they positive. Read between the lines.
From the outside this particular case didn't look healthy. The only other academy I know of people involved with struggles massively (third incarnation at least), merged a private with some of the worse schools in the area. Again can provide no valid or evidenced reason, just rumours/gossip.
See what your head and SMT get out of it and also ask yourself how much you trust them. I think that so many of these are individual you should be very objective about your own case.