暑假只快不乐上学只苦不快
[shŭ jiă zhĭ kuài bù lè shàng xué zhĭ kŭ bù kuài]
It portrays dissatisfaction with schooling over the summer holidays. It says the break feels only quick without joy and when school begins again it becomes all misery and no delight, expressing frustration about the fast-passed short holiday compared to seemingly endless days at school which feels monotonous and less exciting for the speaker