The food system is responsible for a third of global greenhouse gas emissions, with the majority originating from livestock. Reducing our meat consumption is thus an important part of achieving necessary reductions in emissions, and reaching children is especially important to facilitate long-lasting changes in dietary habits now and into the future. This study developed dietary scenarios for three public schools in Copenhagen, which were used as cases to demonstrate reduction in greenhouse gas emissions from public kitchens. The scenarios included (i) replacement of all beef with poultry, (ii) replacement of all meat and fish with legumes, and (iii) alignment of food procurement to the Danish Food Based Dietary Guidelines based on the Planetary Health Diet. The effects on emissions were calculated using three different LCA databases. The results showed reductions ranging from 32 to 64% depending on the scenario, the current meal plan at the case school, and the emission factors used. Not surprisingly, the vegetarian scenario resulted in the highest reductions and replacing beef resulted in the lowest. Adhering to the national guidelines will result in reductions in emissions of 39–48%. Significant variability in the results existed between the three databases, highlighting the importance of basic understanding of LCA for kitchens interested in estimating and reducing their carbon footprint while at the same time providing justification for applying multiple LCA databases for increasing robustness.