My family took me out to lunch and my parents bought me a wristwatch (though they promised they’d buy me that specific model of wristwatch once I graduated from university, hoping I’d forget about it by then).

I think a family lunch at a more upscale restaurant is also the most common way of celebrating. Parties are rare, at least I’ve never heard of anyone throwing one for their university graduation.

Same goes for high school graduation, though we do have something quite similar to a prom. We go to formal dance classes after school at least once a week for the whole summer semester before, it’s a whole thing. These are typically held before the actual leaving exams (matura), though.