Sign in sheets. People sign in as they walk in. You stand there and watch. It takes less than 5 minutes. Door is shut and locked once everyone is in, if you aren't there on time, you lose points for missing class. If you attempt to show up at a time that isn't your scheduled time, you lose points. If you sign in for someone else, you lose points. It really is NOT that hard nor does it take that long to get a roll call at the start of a lab. Anyone saying otherwise, is making excuses.
Start slapping people with serious consequences. Not abiding by the rules= honor board violations. Stick to it. Trust me, people will start following the rules then.