I have been praying at school for the past year and a half and I checked the Qiblah with my friends. However, since then, someone has told me that the Qiblah was the other way. Is my Salah prayed so far valid or invalid?
If you prayed towards the first direction after proper searching for Qibla like compass or reliable Qibla application or asking trusted Muslims in the area, or any other way to find the direction of Qibla, then you discovered that it was wrong, then you don’t need to repeat your prayers if the difference is less than 90 degrees.
Wassalam.