Originally Posted By: 22B

ColinsMum, could you recommend some sources of problems in addition to Alcumus. We've almost never had DS7 solving (non-routine) problems at all, yet, as we were just getting him through the basic K-5 maths so he'd have some basic knowledge, but now he desperately needs to be challenged.

Books to prepare for competitions such as Math Olympiad, MathCounts, and AMC, for example

Math Olympiad Contest Problems for Elementary and Middle Schools, Vol. 1
by George Lenchner

are sources of challenging problems.