It's entirely possible that the rules have changed since you had your first SSBI, but unless they changed things (again) the only reason that they would talk to elementary school teachers is if you actually given them as one of your references. The last time I looked at DCID 6/4 it basically said something along the lines of verify education and interview sources if education was your primary activity during the past three years. There's always the possibility that an investigation would be expanded, but I like I said a couple posts back, I don't see OPM going and talking to someone's elementary school teachers and asking for a character reference.