Students who are ready for intermediate grammar can move on to Grammar for the Well-Trained Mind.
If a student is not ready for this level of work, The Well-Trained Mind, 4th Edition (WW Norton, 2016), by Susan Wise Bauer and her mother, Jessie Wise, recommends these as "bridge" year curricula.
- Rod and Staff--Following the Plan
- Hake Grammar (formerly Saxon)--Grammar and Writing
- Voyages in English, Grade 5
You can learn more about these programs on the publishers' websites.
You can also check the Well-Trained Mind Extended Guide, which is kept current between editions of The Well-Trained Mind. https://welltrainedmind.com/the-well-trained-mind-extended-guide/