[susan53]

If you see them frequently, I'd suggest splitting them - alternate lessons for each. They'd probably learn more from one dedicated lesson than two mixed ones. But if you can't, or if you only see them once a week, and it's not an option, you could split them within the lesson :

Divide the lesson in two. Start with the beginner, and for the first half of the lesson work with him. Meanwhile the other is working autonomously on follow up activities from the last lesson. If there's a computer in the room this could be on-line, or just ordinary "pen and paper" stuff.

Half way through, switch over - the beginner works on practice activities for what you've just focused on, while you work with the other.

If the lesson is very long then it might be better to divide it in four or more segments rather than two. But the principle of alternating remains.