"The strings are a fifth apart. A fifth is an interval of five notes, inclusive. GABCD, five notes, is a fifth. DEFGA, five notes, is a fifth. ABCDE, five notes, is a fifth. All the strings are a fifth apart. All you need to remember is the lowest string, G."

Yeah, that's what I told a six-year-old the other day at his first lesson. In fact, three times I told him - and he still didn't get it. I finally told his mother not to bring him again.