It seems you have a very smart kid and thoughtful and competent school team!

My kids attended a school that turned on the fire hose in 6th grade regarding homework and projects. Also, the tests were suddenly challenging for science and history in particular. If you happen to know what the rigor of the other courses will be, it could help solidify your decision. Although the material wasn�t overly difficult, the challenge became out-put, time management and multi-tasking during 6th grade. A good indicator may be if summer homework is assigned.

Also, a 17 in math at 10 is not bad. My son had the same score at 10, received math subject acceleration, and then got a 24 at 11. It may seem like a relative weakness, but she might still benefit from acceleration.
Of course, I�m sure you have more data than Explore only.

I�m glad you have two good choices!