These are all words for a child that attends school.
student a person who is studying in a school, especially an older child: Students are required to be in school by 8.30; (especially North American English) Any high school student could tell you the answer. pupil (British English) a person who is being taught, especially a child in a school: The school has over 850 pupils. NOTE. Pupil is used only in British English and is starting to become old-fashioned. Student is often preferred, especially by teachers and other people involved in education, and especially when talking about older children.
schoolboy/schoolgirl/schoolchild a boy, girl or child who attends school: Since she was a schoolgirl she had dreamed of going on the stage. NOTE. These words emphasize the age of the children or this period in their lives; they are less often used to talk about teaching and learning.
PATTERNS AND COLLOCATIONS • a(n) good/bright/able/brilliant/star/outstanding student/pupil • a naughty schoolboy/schoolgirl/schoolchild • a disruptive student/pupil • a(n) ex-/former student/pupil • a school student/pupil • a first-year/year 9/ year 11 , et cetera student/pupil • to teach students/pupils/schoolboys/schoolgirls/ schoolchildren • student/pupil behaviour/assessment/numbers
MORE ABOUT students
• A student is a person who is studying at a school, college, university, et cetera. • An undergraduate is a student who is studying for their first degree at a university or college. • In British English, a graduate is a person who has completed a first degree at a university or college. In North American Englishgraduate is usually used with another noun and can also apply to a person who has finished high school: a high school graduate; a graduate student. • A postgraduate is a person who has finished a first degree and is doing advanced study or research. This is the usual term in British English, but it is formal in North American English and graduate student is usually used instead.