I just bought 3 black tetra fish....?

I just bought 3 black tetra fish to take with me to school. I was wondering how I might be able to transport them from home to school tomorrow. I was wondering if i should keep them in the store bag until I get to school around 2, or if I should set up the 1 gallon aquarium I bought for them tonight and then put them back in the bag tomorrow for the trip. How long can the fish stay in the bag? I remember when my family had an aquarium that when we bought new fish we put the store bag into the tank until the bag water temperature became the same as the take water temperature. About how long does that take? Thanks for all your help.