The first thing that you should know, is that an overstayed visa never goes unnoticed. The immigration authorities have registered in their databases every person that enters and leaves the Schengen, and every overstaying, even just for a day, is recorded.
Secondly, intentional or unintentional, no overstaying is left unpunished. It could be fine, immediate deportation or even getting banned from entering the Schengen Zone for a specific amount of time.
Finally, yet importantly, it does not matter if you have entered Schengen territory on a Schengen Visa, or if you are the national of a country, to which a visa waiver has been applied. You are not allowed to overstay the 90 days amount of permitted stay per 180 days, even if you belong to one of the latter. It does not also matter if you are overstaying a Schengen tourist visa or you are overstaying a student visa. There is a visa overstaying penalty for each, and if you do such a thing, you will get yours.