He wants to motivate his pupils and help raise awareness of the Teach for Austria campaign Meine Spende macht Schule (My donation goes to schools).
Money raised from the campaign will go towards training fellows to teach at Neuen Mittelschule schools, which typically have many students from disadvantaged and impoverished backgrounds.
Horowitz, who is originally from the UK but has lived in Vienna since 2010, is keen to give his students something to aspire to, and wants them to be able to think positively about their future.
The Neuen Mittelschule are for children between the ages of 10 to 14 years old and typically over 95% of students are from immigrant or refugee families - and many don’t speak German, or English, very well.
The U-Run, which has never been done before, will take the form of a relay race - with Simon attempting to run at least three metro lines, or 50km.
He and ten other teachers will set off from Heiligenstadt, at the top of the U4 line, at 3.30am. They will follow the U-Bahn network overground, and will be joined or replaced by other teachers at various stages of the run.
At 2pm students from different Neuen Mittelschule across Vienna will join a group of teachers at the Donaustadtbrücke and run or walk a short stretch of 4.5km along the river and through the Prater park.
Horowitz wants to show the children that sport can be fun and that they can achieve their goals. “Anything to get them away from their routine of McDonalds and Playstation,” he joked.
The run will finish at Karlsplatz - and anyone is welcome to join for part of the run if they wish.
The Heinzel Group has promised that if Teach for Austria can raise €100,000, they will double it. So far around €55,000 has been raised.