Just as one may find freshmen and graduate students taking the same college course, so, too, with Sonlight® programs. Your choice of "year" should be based more on content than on the number we happen to have attached to the program. You may wonder how this can be.
The primary reason: Great literature (unlike most textbooks!) is appropriate for a wide range of ages. I have a master's degree. I have been fascinated and educated by materials in the Sonlight Curriculum Kindergarten program.
Our daughter, a straight-A student according to classroom school teachers, studied the Sonlight F program to good purpose when she was in eighth grade. Other parents have told us much the same thing: each program can be used with little difficulty by students with a broad range of ages.
Truly, what is more important: your child's knowledge base, or the number someone happens to have placed on a curriculum guide? We adults don't choose the books we read and the courses we take based on an arbitrary number; why should we choose in that manner for our kids?
If your children have not studied the most spiritually needy peoples and places on earth (the subject matter of our level F program), it's time they did — whether they're in fifth or ninth grade.
So what does all this mean to you?
It means that you'll have the flexibility to do what's best for your family. You could use unique programs for each child, but you also have the choice of using one program for two or more children. Which ultimately means that you save the time you would have spent juggling the extra program(s), save the money you would have spent on it (them), and avoid much of the frustration that comes from being pulled in multiple directions.
One word of caution: there are no hard and fast rules about what will work best when using one History / Bible / Literature program to teach more than one child. To see if Sonlight will meet the needs of your specific situation, ask those who have already done what you would like to do. Visit the Choosing Forum to meet other homeschoolers and draw on their wealth of experience. I'm confident that you'll find someone who can provide you with the guidance you need.
Remember that Sonlight's literature base gives you great flexibility. Capitalize on it! You have the Love To Learn Guarantee. If things really don't work out, return your program for a full refund.