In Britain, a child's progress through the school system is measured by year numbers. School attendance is compulsory from the September after a child's 5th birthday until the end of the term after their 16th birthday.
A new pupil will be in Year 1 and a child who leaves at 16 will be leaving Year 11. 'O' levels have been superceded by GCSEs now, and these are sat in Year 11. If a child stays on at school for A levels these are sat in Years 12, 13, and 14 (at the end of year 14 a pupil is approaching 19 years of age).
So your Secondary 5, allowing for the later start, educates children of the same age as UK Year 12, the old "first year of sixth form" of my day (40 years ago).
Quote:I was told that in England some universities are referred to as polytechnics. Is that true?
Not exactly. Before 1992, you could study for a degree at a university or a polytechnic college. In that year 38 out of the 39 UK polytechnics were awarded university charters and changed their names. So some UK universities. I suppose, are former polytechnics.