In nearly all subjects at least some of the assessment is carried out internally by teachers, who mark individual pieces of work produced as part of a course of study. Examples include oral exercises in language subjects, projects, student portfolios, class presentations, practical laboratory work, mathematical investigations and artistic performances.

Some assessment tasks are conducted and overseen by teachers without the restrictions of examination conditions, but are then marked externally by examiners. Examples include world literature assignments for English, essays for TOK, and Extended Essays. However, externally marked examinations form the greatest share of the assessment for each subject.

The grading system is criterion based (in other words, results are determined by performance against set standards).

Each Group 1-6 subject is given a grade from 1 to 7 (7 is the highest). The Extended Essay and TOK together add another 3 points giving a potential total of 45 points. 24 points are necessary to earn the diploma.