why not a life cycle
like start with oothca photos and tell them what it is and how many nymphs to exspect
choose a male and female
then photo each stage nymph and tell the diffrence from the last stage
then show the diffrences between male and female at adult stage
(at some point describe what they eat and or show photos of them eating)
then if its highschool show the mantids mating then then female eating the male (only cause it happens in nature) then photo a solitary gravid female
then photot the laying of oothca and finaly a picture of then hardened oothca to complete the life cycle
now that ive done all of your work for you have fun
oh and you might have on display with all your work some nymphs and adult mantids . heck you might even be able to sell some at the fair.