The What Works Clearinghouse was established in 2002 as an intiative of the U.S. Department of Education and provides scientific evidence for what works in education.
A couple of Practice Guides that elementary and middle school ESOL teachers may want to check out are listed below:
Assisting Students Struggling with
Mathematics: Response to Intervention
(RtI) for Elementary and Middle Schools
Assisting Students Struggling with Reading:
Response to Intervention (RtI) and Multi-Tier
Intervention in the Primary Grades