Extra-curricular activities generally include various clubs or sports that usually gather after school, or work.
Some examples of extra curricular activities for high school students in the States are:
FLBA and FFA among other TLAs and ETLAs
Junior Varsity and Varsity Sports, football, basketball, etc.
Various high school sponsored band and vocal groups (though these are usually incorporated into the regular curriculum as well)
Activities that usually occur after work: