Is it ever directly stated in the show or manga how high the net is? Otherwise, is there a way to extrapolate it, or is there any information on Japanese high school net heights?
I don't know if Haikyuu!! ever specifically talks about it - it doesn't come up in the anime through the end of season 2, at least - but the net height for high school boys' volleyball is reportedly 240 cm. (Contrast 243 cm for pro men's volleyball, and 220 cm for high school girls' volleyball.)