MTSS stands for multi-tiered system of support. It's a framework many schools use to give targeted support to struggling students. You may also hear it called the MTSS framework, the MTSS process, or the MTSS model.
MTSS is designed to help schools identify struggling students early and intervene quickly. It focuses on the "whole child." That means it supports academic growth, but many other areas too. These include behavior, social and emotional needs, and absenteeism (not attending school).
The tiers of support are a huge part of MTSS. They get more intense from one level to the next. For example, a child getting small group interventions may need to "move up" to one-on-one help.