A 40-minute class is commonly referred to as a "40-minute period" in Engpsh education terminology.
来源：在英语教育术语中，每节40分钟的课程通常被称为“40分钟课程”。
Example sentences:
Today's schedule consists of six 40-minute periods.
Our school day starts with a 40-minute homeroom period.
翻译：
今天的日程安排由六节40分钟的课程组成。
我们的学校日由一节40分钟的班会课开始。