Good teachers use the data they accrue from the assessments they administer to inform their instruction moving forward – namely, what objectives they will need to re-teach.
Bottom line: You need to re-teach what your students didn’t learn. And the only way to see what your students didn’t learn is by analyzing the assessment data.
Below are some excellent resources that detail the importance of using assessment data to inform what you need to re-teach, as well as how you should re-teach, and why the process is essential.