Districts that don't use an agency generally pay more. Those agencies aren't in business for nothing - they are getting a cut. The district is convinced to go with them because of the numbers they have, and the fact that they no longer need to hire a dedicated sub caller. Subs go with them because they can see multiple jobs on their computer. Subs were making $100/day without the agency, but only about $70 with the agency. Additionally, credentialed teachers used to get $150/day for longer term sub jobs, but the agency only pays $120. Where do you think the extra money has gone to?