Multigrade teaching is that where in-: 

Multigrade Teaching: It refers to a teaching situation where a single teacher has to take responsibility for teaching pupils across more than one curriculum grade within a period of time.

• Multigrade teaching is a situation in which one teacher has to teach many grades, all at the same time. It happens in all schools where there are more grades than teachers.

Key Points

Characteristics of Multigrade Teaching:

• A Multigrade class consists of children of different grades/levels, age groups, and ability levels.
• More grades are combined and made to sit together in the same classroom and are taught by a single teacher, and such classes are known as Multigrade classes.
• It combines students belonging to a different grade so the interaction between and within grades is easily possible.
• A teacher teaches many grades at the same time.
• A variety of methods are used to meet the needs of individual learners.
• Peer tutoring is employed, older learners serve as teachers and role models.
• Fewer children are frequently in multigrade classes, but there are different ages in different grades, and students have different abilities.

Hence, it becomes clear that multigrade teaching is that where in a teacher has to teach the students of more than one class at the same time.