The problem of this study was to determine the pupil control ideology—conceptualized as a continuum from custodialism to humanism—of principals and teachers in public elementary schools in the province of Sukhothai, Thailand. The instrument, the Pupil Control Ideology Form (PCI Form), consists of twenty likert-type items. Responses to each statement are indicated on a five-point scale, ranging from "strongly agree" (five points) to "strongly disagree" (one point). Scores derived from the PCI Form were used as indicators of respondents' orientation toward the control of pupils in elementary schools of Sukhothai, Thailand. The reliability coefficient of the PCI Form yielded a Pearson Product Moment Coefficient of .91 and .95 when using the Spearman-Brown formula. The instrument (PCI Form) was translated into Thai, validated by six judges who were selected on the basis of their positions and knowledge of Thai education. The reliability of the revised questionnaire was determined by a pilot study (test-retest technique) which involved twentyteachers and ten principals of public schools in Sukhothai, Thailand. The results of the Pearson Product Moment Coefficient gave the correlation of .87 and .93 using the Spearman-Brown formula.