You might see "the grasshopper has two antennae" in scientific writing. It might also appear as "the grasshopper has two antennae." Greek forms are rarer than Latin ones, yes. I suppose you could do paideai.
A quick Google search reveals that the word has appeared in publications in almost every possible spelling form, including Latin, transliterated Greek and hybrid, in combination with any of the possible plural endings: Greek, Latin, or Spanish/English.
As the word itself is rarely used, no binding conclusions can be drawn on the "commonly accepted usage", so you are free to choose from anything that's on the menu:
... and so on.
Imho, if you don't like paideias, the "pure Greek" form paideiai, suggested by Scrabulista, looks most plausible to me.