The depth of BFSU is in addressing and having your kids master and connect the basic idea(s) and concept(s) presented in each lesson. There are no BFSU lessons that don’t aim at presenting a basic idea or concept. Therefore, with you older child, I would follow the same path as recommended in the text. That is starting at the top and moving back and forth across the flowchart working your way down. However, older kids with their greater background of experience will be able to move through the early lessons much more quickly, pausing to take more time with anything new and not familiar. This is not sacrificing depth for speed. It a matter of helping your kids refresh, organize, and recognize the significance of what they are already familiar with. Thanks for the question, Bernie Nebel