How do you dress when attending a Finnish graduation?

[Ninja]

I'm not really familiar with many of the ceremonies of Finland as I've only been here a number of weeks but it looks to be surprisingly quite formal judging from the pictures online, I've been invited with my girlfriend to attend her cousins graduation from highschool.

I'm wondering what the "dress code" is for men to these events, I wasn't able to bring very many dress clothes, just some nice shirts but no slacks on my trip over here. In the US you can dress anywhere from plain clothes to formal depending on the school and level of education they are graduating from...highschool is fairly informal here for public schools but still somewhat dressy, the students of course are always dressed up but not the attendees so much all of the time.

I've seen a birthday party here for a man in his 40's, and people were dressed like they were about to board the Titanic...so I'm wondering If I should be prepared this time as I anticipated that would be quite casual attire event but was wrong, they even had some fancy cake there, men wearing suits, women wearing dresses.

So should I go down to Dressman and buy myself some slacks and a tie at least to go with a dress shirt? or since I'm a nobody/foreigner, should I just dress somewhat nice (jeans, collared shirt) and leave it at that?

Thanks.

[rinso]

Highschool graduation is one of the main events in a young persons life. (conformation, graduation, wedding)
A little bit of style is appreciated. So suit is good, but when it is warm, shirt and tie could do.
Jeans not so much.

[Pursuivant]

Dressman, you probably can score a jacket too. Otherwise they take a picture of you and put it on walmartpeople.com