Tips on homework help

Does anyone have any tips to help children with homework? We have a Kindergartener and a 4th grader. I bought flash cards to help our 4th grader with math and that’s working out good but our Kindergartener is having issues with basic shapes. It’s getting very frustrating because no matter how many times we go over one shape he can “forget it” 30 seconds later

Any tips so I’m not losing my sanity and upsetting him? Because once he’s upset he closes off from the world and I don’t want to hinder his learning.