I see RTI and MTSS, broadly, as attempting to answer this question:
How do we react to student failure?
What are we, as a school community, doing to prevent/respond to struggling student learners?
My suggestion is to implement a schoolwide system in which we communicate to All Learners that, while failure is perfectly normal for anyone taking risks, we Do Not Let Learners Continue to Fail.
Waiting until the end of a quarter/trimester to begin the intervention process is too late. I suggest that at the end of every learning week (Fridays), a list is pulled of All students failing a class. To make this sustainable, perhaps only certain classes are pulled in the beginning of this initiative, such as Math and Reading. It is those students that would have the opportunity for additional learning and assessment retakes the following Friday.
This looks like having schoolwide interventions in place for when any student fails. Examples include ...
Multiple Assessment Retake Opportunities
Lunchtime review sessions
Before School Review Sessions
After School Review Sessions
Students Missing an Elective for Additional Instructional Time
Flexible Student Scheduling Based on Student Instructional Needs
With this system in place, we are communicating to students that in this school, failure is not an option. WE BELIEVE IN YOU!
What are we communicating when we let students chronically fail?
How can we assist students if in the moment interventions are not in place?
RTI and PBIS are much more effective when done in each, individual classroom. This provides flexibility and opportunities for students and teachers to create their own, individual interventions and incentives based on their own, individual content and styles.