The purposes of this research were to study and compare the condition of internal education quality assurance of schools under Chanthaburi Primary Educational Service Area Office classified by the working and school sizes. The samples used in this research were 30 administrators and 302 teachers in schools under Chanthaburi Primary Educational Service Area Office. The research instrument was five rating scale questionnaire with reliability at 0.97. The data were analyzed using percentage, mean, standard deviation, t-test and One-way ANOVA.