How are you adjusting reinforcement to reduce late arrivals and to increase on-time arrivals?
What are some reinforcing consequences you can deliver either immediately after the student arrives on time or after the student applies a time-management and organizational strategy that will support on-time arrivals?
If the student struggles to arrive on time (and some portion of this is attributed to low motivation), a checklist used to earn points or a reward might be necessary to initially motivate the student. Your ultimate goal would be to fade out this type of system, and to emphasize the natural consequences of on-time arrivals.
Positive reinforcement such as a thumbs up or verbal praise is appropriate if the situation allows this and it does not bring undue attention to the student. Otherwise, praise later in private would be appropriate.
Are you using labeling and social praise to make the contingency between desired behavior and reinforcing consequence clear to the student?
What reinforcing consequences can you arrange that are more naturally or intrinsically connected to arriving on time?
There are a variety of naturally reinforcing consequences that you might emphasize: Getting a desired seat (in class, at a community event, etc.), finishing all work during the scheduled period so that it does not carry over to leisure time, socializing with peers before the work period begins, getting a better parking spot, etc. For some students, it may also be necessary to arrange naturally punishing consequences such as detention, losing points off of partially completed assignments, carrying classwork over to homework, reprimand by supervisor, staying late at work or staying after school to finish an incomplete assignment, etc. As always, be careful in the intentional use of punishment contingencies. Reinforcement should always be more frequent than punishment.