I've been following schooltool on and off for the past couple of years. Their vision for what they wnat to achieve is brilliant, but they've become rather bogged down in the calendaring/scheduling side of things, and whilst this aspect looks very good, I don't think there's been much progress on other aspects of school administration.
Centre looks interesting, but I think there may be more mileage in working up from a Moodle base rather than linking across to different products.
The commercial suppliers in the UK have, AFAICT, made the mistake of producing VLE products which 'talk to' their existing MISs, at little more than the import/export level. The time is ripe for a fully integrated solution, which can pull scheduling, resources, assessment and notes all together and give a clear overview of how a pupil's doing, and what the pupil's doing.