What useful practice has not its dangers?
One of these is, that the teacher will allow these arrangements to take up too much time.

He must guard against this.

I have found from experience that fifteen minutes each day, with a school of 135, is enough.

This ought never to be exceeded.
Another danger is, that the boys will be so engaged in the duties of their _offices_ as to neglect their _studies_.

This would be, and ought to be, fatal to the whole plan.