In some cases, Tier 3 is considered to be special education, with instruction being provided to individual students or small groups by special education teachers "in place of" general education instruction (rather than as a supplement). Initial goals are established through an individualized education program (IEP), which is guided by the results of a comprehensive evaluation, and ongoing progress monitoring helps to direct the teaching process. Special education instruction likely will be considerably longer than the 10 to 12 weeks of supplemental instruction delivered in Tier 2 and beyond. The frequency of special education instruction depends upon student need, and the criteria to exit special education are specified and monitored so that placement can be flexible.