In 1918, an epidemic of the Spanish flu severely affected the population in Slovenian lands. The deadly wave of this disease has captured the Austro-Hungarian lands in the autumn and winter of 1918. Only an approximate, unreliable number of illnesses and deaths are known, but simultaneous sources indirectly reveal all the dimensions of this illness, which had a high mortality rate. The research is difficult due to the complex geopolitical situation in the years 1918/1919, since the epidemic broke out at the very end of World War I, when also the Austro-Hungarian Empire disintegrated and the State of Slovenes, Croats and Serbs was created. Preserved reports of district boards to Provincial government in Ljubljana show that students and teachers in different schools developed signs of the flu. Different district boards in Carniola reported about suspension of classes and closing of schools. Class attendance was varying in different places and schools, namely between 16%-75% of all schoolchildren. In Ljubljana for example, in early October 1918, all schools were closed by the order of the town council. Later all secondary, public and private folk schools and kindergartens were closed until 3th November. The mortality of schoolchildren and teachers in Ljubljana due to the Spanish flu will be shown on the basis of school chronicles and death records.