The mission of the Illinois Junior Academy of Science is to present science as a rational observation and systematic investigation of natural phenomena; to stress the importance of critical thinking and logical reasoning; and to encourage students to view science as an interdisciplinary study applicable to society and its interactions with the environment.

The Illinois Junior Academy of Science exists to for the benefit of students in the state of Illinois, by guiding them and hosting several science expositions throughout Illinois, which culminate with the State Exposition. The process students follow when participating gives them insights into the problems faced by scientists and methodologies scientists use. It encourages students to find information concerning new investigations and discoveries in science. It allows students to get experience with scientific equipment, while also allowing them to develop their own investigation beyond the classroom and progress towards a career in STEM.

IJAS By-Laws