A student is marked as skipped in 2nd hour but is sitting in your 4th hour class - do you do anything?

It depends.  If there is nothing in the In field that shows he has been checked back in since 2nd hour, then the answer is Yes.  You must send him to the office to be checked back in.  This must be done before the next period so the next teacher will see that he has been checked back in and will expect him to be in her class.  If there is a code in the In column indicating that he has been checked back in by the office since the last Skipped code was entered, then you don’t have to do anything because the system shows that he should be in your class.