ELD, or English Language Development, as the name of the strategy entails, is the formal teaching of English to English Language Learners (ELL) in a way that is systematic, methodological, and for the development of skills in acquiring the language, from a beginning level to an advanced level. The ELD teacher will promote the growth of EL skills through
- graphic organizers
- quick checks for understanding
- games, cooperative learning
The purpose of ELD is to make students proficient in English. The skills acquired are beneficial in that they:
- are geared to develop fully-bilingual students
- teach language the "proper" way i.e, expecting correct spelling, grammar, etc
- make the student proficient in both their natural and their target language in both, reading, writing, intonation, and speaking.
The problem with ELD, as others may see it, is that the ELD skills follow their own standards by state. What this means is that the lessons are not always cross-curricular nor connected to other areas of study. Therefore, while the student "understands" the language, he or she may not be able to apply it conceptually to another area because ELD is taught basically in academic isolation. This does not mean that the teaching is isolated itself (the teacher may create activities that tap on other academic areas), but that the purpose of ELD as a strategy is to learn English, not the application of English throughout the curriculum.
SDAIE is another strategy very similar to ELD in terms of execution. Like ELD, SDAIE uses a myriad of visual and kinesthetic resources to aid the student in the understanding of English. However, SDAIE is formulated for application in content, and not just in language skills. For instance, a teacher may develop a Project Based Learning activity where the student is immersed in the different tasks. The student will not learn the English terminology formally, but as he performs the different actions. It is a passive and natural way of understanding, but keep in mind that SDAIE students should be either intermediate or advanced L2, that is, it to apply a SDAIE strategy to a novice L2 learner might be too much... although research shows that, if done properly, immersion can be effective even in a technical environment.
There is no "con" in the use of SDAIE in the classroom, except for the fact that the teacher rapport with the student, the teacher's own personality (patience, willingness to understand, flexibility, wish for student to succeed). Also, the teacher must be very good in content, knowledge, understanding, and technology to be able to assist the student and to use the proper vocabulary. If a teacher lacks knowledge or understanding in content, it would be a disservice to the student. Another important characteristic that differentiates SDAIE from ELD is that SDAIE can be used all day long whereas ELD is meant to meet one goal, which is to graduate the student as an English speaker, and then release the student back into the regular classroom.
In all, although both strategies serve a good purpose, they mainly complement each other especially when it comes to intermediate and proficient L2 students. Using both as interventions at this level is the best that can be done for an ELL.