Ressu is one of the most difficult upper secondary schools to gain entry to in Finland, with admission typically requiring grade point averages above 9.3 on the Finnish scale of 4.0 (the lowest) to 10.0 (the highest).

Students in Ressu have a reputation of moving onto illustrious careers in further education, in a range of top universities both in Finland and abroad.

The school was founded in 1891, at which time it was called Helsingin Suomalainen Realilyseo (the Helsinki Finnish Real Lyceum) and at which point it only taught male students.

The teaching concentrated on broadening the previously strict and narrow subject areas, that were held mostly in Latin, to also include other languages as well as a selection of sciences.

[citation needed] In their second year the students also have the possibility of partaking in Vanhojen tanssit (resembles the U.S. equivalent of prom), and perform traditional ballroom dances in the White Hall (Valkoinen Sali) in the center of Helsinki, next to the Presidential Palace.