Row Level Security in Excel (Saved on Sharepoint)

To the best of my knowledge you can't achieve this directly in excel with out Power BI licences.

Some alternatives:

1) Look at storing data in sharepoint lists. You can control acces to rows there (https://sharepointmaven.com/2-ways-to-manage-row-level-security-in-a-sharepoint-list/). Not really sure how scalable that is though.

2) If the data is in a sharepoint list you could wrap a power app around it. I believe for free if using a non premium connector like sharepoint. You have to fiddle permissions to "hide" the sharepoint list but can then embed security logic in power apps which is more scalable.

3) It sounds like you work in education so worth speaking to your IT team. I know ours have versions of on prem sql server/analysis services included in their licencing packages. Might open some options in terms of using excel.