What is CCSS?

CCSS most likely refers to the Common Core State Standards. These are educational standards in mathematics and English language arts/literacy (ELA) that outline what students should know and be able to do at each grade level. They are used to guide curriculum development and assessment in many US states. They aim to provide a consistent and clear understanding of what students are expected to learn, so teachers and parents know what they need to do to help them. Note that these standards are controversial and not universally adopted.