Block Codes
A Block code is an optional field on a Placement Group. 

The Block Code can be used for two purposes:

1. To help ensure a student is put into only one placement group at a time.  
2. To group together placement groups for searching and reporting.

When adding students to a placement group, by default the checkbox "Ignore students in current block code" is set.  

If students have already been added to a different placement group with the same Block Code, they cannot be added to this one.