A lecturer should arrive ahead of the scheduled time to set up the lecture aids and be present when the majority of the class arrives. One or two may be okay, but a larger group should be tackled so that the problem does not recur in later lectures. An astute lecturer will be aware when students are late due to a test or an assignment deadline imposed by other courses but this should not impinge on other lectures. One solution is to ask the class if they would like to start each lecture at 5 minutes past the hour. Invariably they will support you in starting sharp on the hour.
Punctuality also applies to deadlines for assignments.
There is no point in setting a deadline unless it is to be observed, regardless of when the staff intend to mark the assignment. Students will soon decide whether to pay attention to the deadlines. When a deadline is set, it should specify a date, a time and a location, consistent with the opening times of the venue. It should be enforced to the minute. Students can be given a clear but fair penalty for being late.