So how do you know whether it's worth it to test for the hg+ programs?

There is a local HG+ charter school that seems amazing, low/no pressure, totally individualized curriculum and it's free. I'm considering trying to get DS4 in since he starts K next year. Then if he gets in DS6 would get priority (if he gets the scores necessary). But, I just worry that this is all a waste of time and while the programs sound amazing they aren't for my level of GT kids.

DS4 is working at a K/1st grade level right now in math and reading, probably 2nd grade+ for science. It's more his abstract reasoning and visual-spatial abilities that amaze me though. He can come up with a solution to any problem, we regularly hear "actually, you could" followed by the most hilarious explanations of how you could make it so. He loves word play and makes the best puns! He is really good at jigsaw puzzles.

DS6 is homeschooled and working at end of 3rd grade in math, 5th/6th grade reading, and probably somewhere around 4th-5th grade in science. Math is the only place I've nudged him and even then it's been at his pace, just not necessarily at his request. Reading and science have been totally his doing. When we pulled him from Kindergarten 7 months ago, besides reading, he really wasn't working very far ahead.

So, how do I know if they're HG+ or just regular old GT, but are ahead because they have the opportunity to move at their own pace due to homeschooling? I feel like I just got ok with knowing they were GT and now I'm right back to where I was but worrying about level of GTness.