Does a school still need to upload its attainment data onto the ISI data portal?

No, the school’s analysis of the progress and attainment of pupils will be requested by the reporting inspector once the school has been notified of its inspection. 

This data can be supplied in any form and will be discussed with school leaders on inspection.

This means that schools no longer need to use the ISI data portal at all. Legacy data will be deleted at the start of January 2024.