Hi

This limitation is by current design.

You can however vote for this on our idea scope to assist in getting enough votes to help assist getting this change more recognized by the development team.

https://www5.v1ideas.com/TheSageGroupplc/sage300erp/Idea/Detail/38207

As it is a limitation in Sage DB and Application, So you can Optional Field for Student No. 

Hi Faisal. Yes. You can use Optional Fields.

Not friendly to use optional field because two or more students can have a same registration number (optional field) without prompting an error

Not friendly to use optional field because two or more students can have a same registration number (optional field) without prompting an error

The registration number can twigged and changed slightly, else have a look at a pure School Software designed by one of our ISVs.

Hi Patty, kindly share the name of ISV or software

Use Extender Developer (by Orchid). it will help you.

it will provide you a prompt once it will find duplicate registration number in the values of Optional field.

Hello Patty,

Did you forget to share or did you perhaps share via Inbox the information about School Software?