If a class which most classes do, builds upon previous material, then it is paramount that most students understand the standards before moving onto new material. This is a perfect example of when differentiation should be use. For the students who have mastered the material, alternative lessons should be given to them that could be independent research work while Ms. Lewis works with the students who need more instruction.

If Ms. Lewis dedicates time each day for a daily warm-up or "do now" she could incorporate the material into her class during this time. This way it would not be taking any other time away from the new unit, but the students would still be receiving and revisiting the information from the previous unit.

Ms. Lewis could serve these times during an intervention block, or she could serve these students in a math or reading workshop (depending on the core subject). During workshops, activities are leveled based on student needs. She could also have differentiated groups with each group having a basket. In each basket, she could always have a review task and a skills practice for the current standard they are working on.

If more than 80% of your students have not met the standard, reteach is extremely important. You cannot follow a generic pacing guide and continue with the content if the students have not understood what was previously taught. I would suggest doing back and providing that information through spiral review at the beginning of each class period. Take time to go over each question and provide feedback as you go. Then slowly move on to the next topic.

Ms. Lewis can offer before or after school tutoring for those who have not yet met the standard. She can also utilize computer based programs and have the students work through them on their own.