According to the book, the factors that must be taken into consideration are the state a federal policies, the strength and need of the class and desire and interest of the student. Individual difference is also an important thing to take note of. No single model is perfect for all ELL students. English is a very dynamic language. Pull out model effective as there are small groups and instruction provided is also fruitful. I do feel that if applied correctly these models are appropriate and effective. The push-into model has been effective in classed where the number of students is large.