Most of the class is/are very smart.

“Most of the class is/are very smart.” Are both “is/are” correct in combination with “class”?

‘Is’ and ‘are’ can be correct depending upon whether you are referring to the class as a whole unit (is) or to individuals within the class (are).

In your example, the correct verb is ‘are’ because you have used ‘most of’ (which splits the class up into individual members).

The class is full of smart students.
Most of (the students in) the class are smart.