It is generally agreed that school assemblies can be successful and, if they are, are worth while for pupils and teachers and for the school ethos; and I suspect time spent in religious observance is felt to be worthwhile to those who are religious. But to assume the former can only be achieved by turning them into the latter is a non sequitur.
The document governing religious observance in schools in Scotland (Circular 691) makes no link between any act of religious observance and assemblies. So schools would appear to be entirely free to hold separate, non-religious assemblies.
Alan Henness Humanist Society of Scotland Lumley Street, Grangemouth