Yes, in our stand-alone TAG school there is differentiation in each classroom.
Math: students are tested and placed in math classes. Students who are high achievers in their math classes are given additional projects to do.
Reading: all done on an individual basis. Students read, log what they have read and journal about it.
Spelling: students are grouped. Lowest group in each room is usually two grade levels ahead of typical grade level classroom. Top spellers are given Latin and Greek so that they can learn root words.
Science: Not that I have seen. It is mostly hands on work.
Social Studies: Not that I have seen.