Of course there is no such thing as criterias. Nor are there maximas or minimas. If you had had the opportunity to have Latin in high school you would know that the word form ending in -a designates the plural form, while the -um designates the singular. Criterion being an exception, probably because the language has changed over time from criterum to criterion.

But really, it has not much to do with whether or not you had Latin. It is like everything, you learn it and then you know it and use it, or you do not. True, you might say this is easy for me to say because as a German I grew up with all sorts of irregular articles, genders, and word endings, but that argument is not airtight.

If people would form the plural according to proper English grammar, then the plural of minimum would be minimums, the plural of maximum would be maximums, and the plural of criterion would be criterions to stick to the examples given above.

But this is not what I hear everyday. The words criterion, minimum, and maximum are all but extinct. Instead the plural form has become the new singular of which the new plural is formed by appending an s. Also, this phenomenon is not limited to English speaking folks. In Germany I heard quite a few people refer to Minimas and Maximas; the plural of Kriterium, Kriterien, still seems to be used properly, but that may have changed in the last 10 years since I moved to the US.