Looking first at upper-secondary schools, teachers in the USA spent the largest amount of time teaching, accounting for 1200 hours. The figures for Iceland and Spain stood at 900 hours each. Japanese teachers, meanwhile, dedicated the smallest proportion of their time to teaching, at 700 hours.
As for lower-secondary schools, the figure for the USA would again top the list, with teachers in this country spending 1000 hours completing their professional tasks. Spain followed closely behind, constituting around 750 hours, while teachers in Japan taught for roughly 650 hours and those in Iceland 50 hours less.
American primary-school teachers, at the same time, worked for about 750 hours while their Spanish counterparts recorded around 670 hours. The figures for Iceland and Japan were fairly similar, with respective figures of 590 hours and 600 hours.
In summary, there appeared to be a correlation between the amount of time spent teaching and the types of schools in all the nations cited in the question: the higher the education was, the more time was allocated by teachers for educating. Of particular note is the figure for the USA, which commanded the lion’s share across all the school types observed.