We aimed to identify empirically valid cut scores on the positive behavioral interventions and supports (PBIS) Tiered Fidelity Inventory (TFI) through an expert panel process known as bookmarking. The TFI is a measurement tool to evaluate the fidelity of implementation of PBIS. In the bookmark method, experts reviewed all TFI items and item scores by difficulty in order estimated by an item response theory (IRT) model of TFI data. Over two sessions involving data review and discussion, panelists individually identified which corresponding cut scores in each TFI tier scale indicated minimally adequate fidelity in the TFI, leading to corresponding scores of 83.3% for TFI Tier 1, 84.6% for TFI Tier 2, and 82.4% for TFI Tier 3. Then, the proposed cut scores were compared with the original cut scores of 70% for percentage of schools meeting fidelity and the association between the cut scores and school discipline outcomes using an extant sample. The results of descriptive statistics and multiple t-tests suggested that the bookmark cut score in TFI Tier 1 was reachable and more strongly associated with improved school discipline outcomes. Findings for TFI Tier 2 and Tier 3 were less conclusive.