This quantitative study explores the 2010 recommendation of the Educational Funding Advisory Board to consider the Evidence-Based Adequacy model of school funding in Illinois. This school funding model identifies and costs research based practices necessary in a prototypical school and sets funding levels based upon those practices. This study investigates the extent to which Illinois elementary and middle schools are meeting targets identified in the Evidence-Based Adequacy model of school funding using school level data. Analyses were conducted on samples formed with two sets of selection criteria. Criteria A selected schools base on school size, class size, kindergarten programs, and preschool programs and identified 16 of 3,201 schools. Criteria B selected schools based upon only school size and class size and identified a sample of 86 elementary and middle schools. An ANOVA analysis found a significant difference in student achievement at schools identified by selection criteria B. Second, a Chi-squared test of independence determined that the identified samples were substantially similar to the population. A multiple linear regression analysis yielded a significant relationship between student achievement and the identified variables. Both samples showed presence of an assistant principal as having the greatest impact on and negative correlation with achievement. Finally, per-pupil expenditures at schools meeting selection criteria A were significantly less than schools not meeting. There was no significant difference in spending between those that did and did not meet criteria B. This study serves as an initial study of the Evidence-Based Adequacy model of school funding in Illinois. Additional investigation is needed to more completely understand the negative correlation between student achievement and the presence of an assistant principal. There is also additional investigation needed to understand the finding regarding the cost associated with implementing this model of school funding in Illinois. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]