A model is proposed to project optimal school psychology service ratios based upon the percentages of at risk students enrolled within a given school population. Using the standard 1:1,000 service ratio advocated by The National Association of School Psychologists (NASP) as a starting point, ratios are then adjusted based upon the size of three high risk groups (students with limited English proficiency, students eligible for free or reduced lunches, and students classified as educationally exceptional). If the percentage of students belonging to one or more of these groups exceeds the target figure(s), then staffing projections are increased for each risk factor present. Comparing the proposed model to actual staffing practices across the nation, eight states were found to have one or more risk groups above criteria. The mean staffing ratio of these eight states (1:2,459) was higher than the mean ratio of the states that lacked elevated concentrations of at-risk students (1:2,020). Therefore, when the analysis was conducted at the state level, it did not appear as if elevated percentages resulted in lower staffing ratios for school psychologists. Results are discussed in terms of the dependent relationship that exists between staffing ratios and school psychology service delivery models. (Contains 23 references.) (Author/JDM)