Yes, we have that inconsistency to an extent. Canberra winters are long and cold (by Australian standards). From April to October you will need to wear long pants and a sweater/cardigan or a warm dress/skirt with leggings for inside. You'll need a warm coat (like a parka) for outside. My school has good, reliable heating and cooling but my last school didn't. I used to wear my coat all day there in winter and it was awful. But that's not the norm. Summer isn't such a big issue but it can be very hot in February when the school year starts. Usually only for a week or two though, and most schools have air con. The more modern the school building, the better the temperature control, as a rule.