Rearrange the jumbled parts of the sentence into sequence: (P) science and mathematics exhibition (Q) for a discussion on the forthcoming (R) to be present before the Principal (S) all students have been instructed

The correct sequence is SRQP: 'all students have been instructed to be present before the Principal for a discussion on the forthcoming science and mathematics exhibition.' S provides the subject and main verb, R continues with the infinitive phrase, Q adds the purpose, and P specifies the topic.