Satisfactory needs to mean satisfactory

Isn't it great when someone writes a really clever and incisive letter to a newspaper?

Miss Christine Gilbert recently said that schools were let down by too many satisfactory teachers. This resulted in a letter to the Telegraph from Nicholas Bielby of Bradford (which I read in The Week today).

He writes that just as everybody cannot be above average, a good system works with satisfactory people performing satisfactorily – producing good-enough outcomes. There is something wrong with the system if it only works with excellent staff.