Young English-speaking children often omit auxiliary verbs from their speech, producing utterances such as "baby crying" alongside the more adult-like "baby is crying." Studies have found that children's proficiency with auxiliary BE is correlated with frequency statistics in the input, leading some researchers to argue that children's auxiliary knowledge is item-specific and slow to develop. In a priming experiment, we investigated whether 2- and 3-year-old children represent auxiliary "is" and "are" as part of an abstract syntactic frame. We tested whether children could be primed to increase their auxiliary production when the prime and target differed by subject, verb and auxiliary type ("is" or "are"). We found these patterns of priming, indicating children represent auxiliary BE as part of an abstract syntactic frame that minimally contains "is" and "are," despite the frequency-based effects reported in the literature. (Contains 3 tables, 1 figure, and 5 footnotes.)