The two special population groups that you are most likely to have in your classroom include Special Education children, who come with an IEP, and English-as-a-second-language learners. You may have others, also, but these two groups are the most common.
Special Education students are on a specially trained and hired teacher's caseload, and come to you with an Individual Educational Plan (IEP) a legal document that you are required to follow. It spells out the specific accommodations and modifications that the child needs to succeed. Special Ed children come with a huge variety of abilities and disabilities. Gifted children, for example, are also Special Ed, and also have IEPs. Children can be physically handicapped, cognitively (intellectually) disabled or extraordinary, ...
What special student populations are you likely to have in your class as a teacher, and how should those students be addressed in the classroom?