Hello! I'm new here, so I can't give advice on what has worked.
We did not have achievement testing done and are also pulling together a portfolio. I've been reading previous posts and did call DYS. The person I spoke with was helpful. She stressed several times that they really only want 4 examples of work. She also stressed that these should show academic achievement. In light of that, I'm keeping it simple.
Like your child, our DS is young and doesn't produce work samples that highlight his verbal and math skills. I'm sending a video clip of him reading last December (age 4.5) and one current one. Also two math sheets up a couple grades. Also, I've asked his teacher for the assessments they've done in school, which I'll include. Spelling is a strength, so I thought of giving him a spelling test and just sending one math sheet. I suppose we'll see what he's in the mood for this weekend!
