In In re Appeal of Coatesville Area Sch. Dist., the Pennsylvania Supreme Court did an admirable job of differentiating and explaining the two preclusion doctrines — res judicata and collateral estoppel — while simultaneously wading through a procedural minefield laid by unclear rulings in parallel taxation appeals. In this case, a landowner sought to appeal the valuation of his property, and both the local township as well as the local school board sought to appeal the county’s Board of Assessment Appeals’s ruling to the Court of Common Pleas. The township eventually gave up and did not appeal to the Commonwealth Court, though the school district did. The taxpayer convinced the Commonwealth Court that insignificant procedural mix-ups meant that the preclusion doctrines prohibited the school district from continuing its appeal. The Supreme Court reversed, holding that neither doctrine applied.