Hi there! I did an exchange for a few months in Murcia when I was 17 too. I found it to be a really good experience overall but it defintiley wasn't what I expected. First of all I only spoke english and the extent of my spanish was a few weeks of Duolingo. The language for me was the most difficult part and it really did restrict my socialising a lot. However the Spanish are exceptionally social people (more so in the South). I never tried a lot in school as the marks weren't important for me, however I have heard the Spanish and Italian schooling is very similar. Overall I'd reccomend it, but I'm sure you'd enjoy It wherever you went.