Baking powder can get old; to test try this: . . .
take a cup of water and drop a teaspoon of baking powder in it. It should bubble pretty ferociously. If it does not, you need fresh stuff.
Do you think your baking powder is old?
Also, you might want to put fresh baking powder into a glass jar with a steel top for storage. Any moisture will affect the action of your powder, and glass and steel are pretty much moisture proof.
For sure, check on your oven heat. Another rise is oven spring--you need that heat of the oven to make all that gas (that the baking powder created) in your dough expand quickly and help your biscuits rise. Try fresh baking powder, higher heat, and preheat well and see if that doesn't help.
As for flour type, I live in Southern California and have used Gold Medal AP flour, various bread flours and Smart-n-Final (a local wholesale-to-the-public store) AP flour and always get a good rise. I am careful to have a very moist dough, don't over handle the dough, have fresh baking powder and know my oven's temp is on and preheat it well--AND I cook (just to make sure) on a preheated baking stone, which gives a nice crusty bottom too boot!
I have heard though that White Lily (and flours of that type) have a different flavor than the regular AP flours one finds generally. Flavor that is long-time appreciated in the South!--And I cannot get it here. . .
And my disclaimer: with all of cooking, your mileage may vary! smileys/smile.gif