Eton calls its internal examinations 'trials', not to be confused with such things as soccer, rugby and cricket trials in which a boy is assessed for his suitability for a particular team.

Trials take place for all boys during the last few days of the Michaelmas half, from the Wednesday after the annual Founder's Day Holiday (always a Tuesday, but officially a celebration of Henry VI's birthday, December 6) until the morning of the final Tuesday of the half. Papers are marked immediately by masters and each boy receives a printed trials card showing his achievement in each of his subjects on the last day of the half at a meeting with his tutor. He then takes that card, on which the tutor will have written a suitable comment, to his house master, who then forwards it to parents with a boy's other end-of-half reports, a tutor letter, and his own house master letter.

Boys in F, E and D attend a ceremony called 'reading over' before they receive their cards from their tutors. Either the Lower Master for F and E or the Head Master for D reads the names of boys who have achieved merits and distinctions in trials to the whole block, together with the names of boys who have been awarded prizes in particular subjects by heads of department, and perhaps, if one boy has distinguished himself above all others, an overall trials prize.

Boys in F and E and some boys in C taking Pre-U courses also take trials at the end of the summer half.

Results in each academic subject are reported by overall percentage, by position in the cohort taking the exam, and by the individual marks achieved in each paper. Whether an overall set of results qualifies a boy for a distinction, merit, pass, borderline result or fail is determined by the Director of Curriculum in consultation with heads of block, the master in charge of trials, and either the Lower Master or Head Master. There are usually about 75-80 distinctions and merits in total for each block, split approximately half-and-half.

A boy who earns a distinction on three consecutive occasions qualifies for the award by the Provost of the title Oppidan Scholar and has an 'OS' placed after his name; he may also qualify by achieving a distinction four times in total without achieving three in succession. External examinations do not count towards the award of an oppidan scholarship, being regarded as reward in themselves, so the sequence of trials regarded for purposes of the award of an oppidan scholarship as being 'consecutive' are F Michaelmas, F Summer, E Michaelmas, E Summer, D Michaelmas, C Michaelmas, B Michaelmas.