What breed of dog do you think suits me?

Im 15 nearly 16 and I have cats. My parents would prefer a smaller breed of dog and i'd like one that isnt too hard or stubborn when it comes to training. I'd be at home for the next 8 weeks (cause i've finished exams and its summer) then i go into sixth form so a dog that could cope being alone for a couple of hours or would just sleep when left alone would be good. One that wouldnt need much grooming (maybe just a brush every now and then). I'd be able to take it on a walk twice a day and a breed that could be trusted off lead. I was thinking shih tzu cause they're small but i wasnt sure. Thank you:)