Don't supplement with workbooks! Use this time to teach organizational breakdown. Kids in the hgc excel later not necessarily because they are brighter but because they are being taught organization/executive functioning in 4th grade. Most "regular" students won't have to balance a ton of stuff until middle school and that's when bright kids can falter.
Get a planner and a calendar and teach your elementary school student how to plan ahead. That's way more helpful than more math worksheets.

Mom of hgc 4th grader and 7th grader who did NOT get into hgc

Anonymous wrote:Is the non-verbal portion given more weight in admissions?

My understanding is that you have to do well (cross some threshold - that may differ from HGC to HGC) in all 3 sections. How that threshold is determined...that has been the subject of many threads in this forum.