You are a wise lady to consider placement from all angles as you go into the next year!

I don't think 5th. grade is too old for Bigger Hearts with extensions provided that's where the child places well according to the placement chart, but I do think a child that did well with CTC the year before would not be challenged nearly enough by doing Bigger Hearts with Extensions the following year. Sorry - I wish I could say otherwise

- but it would be an incredible step back.

I think you would lose all of the independence your CTC child had gained, and I also think the academic skills wouldn't be growing through the year, but would instead probably be going backwards. Written narrations aren't even done in Bigger Hearts, there isn't a Student Notebook, there is no research, there isn't a writing program, there is no independent Bible Quiet Time, the parent does the history/science readings, the history projects and science experiments and geography are much less mature, etc. I just think you'd wish you could "unring" that bell if you went that route. I also think your 7 yo will really need your full attention as she/he does Bigger Hearts, and your sixth grader would be done in a flash and twiddling his/her fingers impatiently waiting on you as you tried to hurry along little 7 yo pumpkin. I think you'd really enjoy having your older child do RTR, especially as you enter in the middle school years. The Bible Study box along with the puberty study really comes to mind - I just think your conversations with your older child will need to be focused on such different heart (and even body) issues than your 7 yo. I've really found that to be true over the years with our 2 oldest dc - having our Bible times separate sure brings out a deeper, more heartfelt discussion as each child feels "safe" to share his personal struggles (much different than our family Bible discussions). I also think you being totally in charge of your older child's day again (as is the case in Bigger Hearts for the most part) could cause some conflict. I know it would with my oldest, as he's grown to love his independence in certain areas of school especially. It would be tough to take that back from him. Anyway, these are just some thoughts I had about this. You are in the driver's seat here and will know best. HTH as you ponder this!
In Christ,
Julie