As districts grow and change many times old codes are no longer relevant. From a system stand point, you really never should delete codes that have been used anywhere but leaving them in the system means they show up and can be selected by users even if the district decides they don't want to use the code any longer. I'd like to see on all codes in the system an Active checkbox. When the Active flag is unchecked then the code could no longer be selected from drop-downs in the system. This would prevent improper use of codes the district has decided to no longer use. From a system perspective implementing this could be as easy as sorting the valid values by the Active flag so all the inactive flags go to the bottom of the list and then all the values that are inactive could have their HTML disabled property set to true so that they can't be selected and at the same time wouldn't cause errors with historical records that already had those inactive codes selected. There are more elegant ways to implement this but that's definitely the easiest way.