The Scots College was forced to cancel one of its trial HSC exams on Tuesday morning after two papers were stolen in a late-night break-in hours before the exam was due to begin.

The eastern suburbs boys' school is under pressure to expel students if they are found to have been behind the heist, which saw two physics papers go missing from a storage cupboard in the school's Bellevue Hill grounds on Monday night.

Scots College is reviewing its procedures for the storage of trial exam papers. Credit:Edwina Pickles.

Scots is one of about 480 NSW schools, public and private, that use trial HSC papers written by the Catholic Schools Secondary Association (CSSA) and it was one of these papers that was stolen. Developed in 1967, the association's papers are recognised as some of the most rigorous exam papers and are seen as good preparation for the HSC.

NSW Police are investigating the break-in and college staff told students on Tuesday morning that the test would be rewritten and rescheduled for next week.