How to handle multiple assessment administration dates for one assessment

We have a use case where we have an assessment that is given to kindergarteners with different objectives usually tested on different dates over roughly 2-4 weeks (because you know, short attention spans!).  We need to be able to store each administration date, by objective score, in the ODS.    StudentAssessment only allows one administration date, with an optional end date, which could encompass the overall range, but not each one.

I only see two possible ways to handle this - 

1 - split the assessment into multiple Assessment tags, unique to each possible administration.   This has the downside of losing the relationship between all of the objectives and the cumulative scores.

2- Use an extension.  More development work, requires XML, ODS database, dashboard and ETL mods.

Am I missing something?  Any other suggestions?   Or feedback which approach would be better?  Thanks for any guidance!