When I was on RAGE they kept track on a sign-in sheet. It allowed us to see how many hours we had put into the program (something sponsors like to know) as well as being able to see when students had left the building in case a parent called looking for them.
Following the change in the
FairPay Act last year our IT jobs were reclassified from salaried to hourly and now we use a simple electronic time card system available
here that allows you to punch in and out, compile reports and log time to different projects. It's very inexpensive and might be a good solution for you.