Security Deposits

Hi ,  I require parents to pay a 25% refundable deposit which is refundable if  a 30 day notice period are met. Can I capture these deposits as security,  upfront deposit or retainer?  These deposits should not be available as a credit balance on the account statement ( to set off invoices against) but should reflect on statement as deposit kept - until parent cancel contract with the school. Kindly advise correct accounting method, thanks