Changes should be carried out "quickly and decisively in all schools in order to bring about positive long-term benefits for all pupils", HMI states in as close to a reprimand as it gets.
An interim follow-up report praised "some encouraging progress" on most of the six points of action called for but added: "A considerable amount of work still remained to be done."
The report issued this week acknowledged improvements in consultation, staff development and monitoring schools to raise pupil attainment. But HMI added that the council "needed to increase the rate of progress in improving aspects of policy development and resource management".
The follow-up visit also found that "the council required to gain the commitment . . . of all staff, to be sure that all pupils within the authority receive the best possible education".
One of the areas in which the Western Isles has "much to do" is in developing a strategy for school rationalisation.