Brake Pedal Low

My son and a friend of his changed the front pads in my Dad's lancer. Now the pedal is very low but can be pumped up (but is low again the next time you hit it). We bled the brakes front and rear but there was little improvement. After asking them about there procedures, I found that they pressed the pistons in without opening the bleeders (I'm not certain that this has anything to do with the problem), everything else was straight forward. The pedal was hard and high before the pad replacement, we only changed them because the state inspection showed they were too thin to pass. Rear shoes weren't touched. Any ideas? Anyone?