Curriculum too easy for one child and too hard for another?

Separate by subject not by year. Read-alouds and history together; maths and phonics split to individual levels.

Same living books, different narration expectations. The 7-year-old narrates orally; the 11-year-old writes a paragraph.

Completely separate the struggling subject. One hour, zero comparison.

The older teaching the younger consolidates knowledge and removes the shame dynamic. Teaching is not the same as struggling.