Background: In this study, we applied behavioral economics to optimize elementary school lunch choices via parent-driven decisions. Specifically, this experiment tested an optimal defaults paradigm, examining whether strategically manipulating the health value of a default menu could be co-opted to improve school-based lunch selections. Methods: The design was a randomized comparison of optimal versus suboptimal (standard) default lunch menus for all first-graders in a school district for a period of 1 week. We hypothesized that making the default lunch option healthier, while providing parents the opportunity to access and choose from the standard school menu for their child, would yield more frequent selection of healthier items than when the default option was suboptimal. Results: Overall, 127 (93%) first-grade children's families participated. Among those families randomized to receive the nutritionally optimized default menu, all but one remained with these options; of those parents randomized to the standard menu (suboptimal default), all parents remained with these options (?[superscript 2] = 123.06, df = 1, p < 0.001). Conclusions: The mere positioning of choices, without restricting options, significantly affected which menu items the children received during the test period. Results are proof of concept for a strategy to increase health-promoting school lunch content, procedures, and policies.