老师的话是最好的摇篮曲
[lăo shī de huà shì zuì hăo de yáo lán qŭ]
It conveys that 'the teacher's words are the best lullaby', symbolizing how lectures can sometimes be boring enough to put one to sleep. This phrase may also imply that what the speaker hears in class often feels soothing to a point that makes them want to drift off to sleep.