A shorthand term for middle-school and high-school students (combined). Used to refer to that age/group.
中高生は夏休みに部活動や塾で忙しくなることが多い。
Middle- and high-school students are often busy during summer vacation with club activities and cram school.
このイベントは中高生向けに無料で開催される。
This event will be held free of charge for middle- and high-school students.
駅前で中高生が部活の帰りに集まっていた。
Middle- and high-school students were gathered in front of the station after club practice.