Olympiad League (OL) is a paid online platform where registered participants in secondary schools compete with each other on Olympiad Subjects like Mathematics (MathOL), Physics (PhysOL), Chemistry (ChemOL), and Biology (BiOL). The season is open from September to May. 

If you are registered to OL you take OLE (Olympiad League Exams) at the end of each month mostly on the last Saturdays at the scheduled time. The sum of 9 OLE exams at the end of the educational year determines the ranking of participants and their awardings. Detailed info is on the following website:

http://www.olympiadleague.org/