Shelly,
Write with the Best should work well for a 7th grader too. It is a program that works well for a wider span of grades. I'd say best for a strong 4th grader through 8th graders. I wouldn't consider it high school level though.
For literature study, we would recommend DITHR Level 6/7/8. The dictation passages within CTC should be enough for a 7th grader. My oldest son is a very good speller, and he was doing the highest level of passages provided within CTC this year and finding it to be enough.
The English schedule in CTC is for Rod and Staff English 4 or 5 at half-speed, so this is one area you would want to adjust to either do English 5 at full-speed or English 6 at half-speed, or your own grammar. This would put you on pace to complete the equivalent of Rod and Staff English 6 (which is very advanced) by the end of grade 8.
Blessings,
Carrie