firebase-remove.js

db = firebase.database().ref('test');

const userId = firebase.auth().currentUser.uid;

function removeStudent(studentKey) {
    db.child('data/students').child(studentKey).once('value', (studentSnapshot) => {
        const student = studentSnapshot.val();
        const courseKeys = Object.keys(student.courseKeys);

        const removeData = {
            [`data/students/${studentKey}`]: null,
            [`data/schools/${student.schoolKey}/studentKeys/${studentKey}`]: null,
            [`users/${userId}/studentKeys/${studentKey}`]: null,
        };

        courseKeys.forEach(courseKey => {
            removeData[`data/courses/${courseKey}/studentKeys/${studentKey}`] = null;
        });

        db.update(removeData);
    });
}

removeStudent('<some student key>');