The Johns Hopkins Center for Talented Youth organizes 3-week summer programs nationwide http://cty.jhu.edu/summer/catalogs.html , both for students in elementary school and middle/high school . Even for parents not sending their children, the course descriptions and textbook lists may be useful .

The Individually Paced Math Sequence http://cty.jhu.edu/summer/mathsequence.html lists books for arithmetic through pre-calculus that I presume are suitable for
the motivated and talented students that take the CTY course:

Arithmetic (topic)
Fundamental Mathematics (book title)
Bittinger (author)
2002, 3rd (date and edition)
Addison Wesley (publisher)

Pre-Algebra:
Prealgebra
Bittinger
2000, 3rd
Addison Wesley

Algebra:
Algebra
Smith
2001
Prentice Hall

Geometry:
Geometry
Jurgensen
2000
McDougal Littell

Algebra II:
Algebra II with Trigonometry
Smith
2001
Prentice Hall

Functions, Trigonometry, Discrete Math:
Advanced Mathematics
Brown
1994
Houghton Mifflin

Analytic Geometry:
Precalculus with Trigonometry
Foerster
1993
Addison Wesley

Comments on these books and suggested alternatives are welcome.

Do you have a link to the science textbooks?

Science texts for elementary school students are listed at http://cty.jhu.edu/summer/catalogs/ys/ysscience.html

and for older students at
http://cty.jhu.edu/summer/catalogs/is/isscience.html .