Exercise the body before the brain
Exercise, even something as simple as 30 minutes of walking, can help with focus on work. With gorgeous spring weather in the forecast, this is a great time to get your child outside. Just skipping the bus in favor of a walk or bike ride home can have benefits.
A lot of research focuses on exercise's benefits for children with ADHD. (See, for example, this article from ADDitude magazine or this WedMD summary.) Yet, there is also evidence that exercise helps typical children and adults function better on subsequent cognitively demanding tasks, like taking a test or giving a speech.
If your child seems distracted or irritable during homework time, try switching up your routine by being active together before sitting down to work. You might be surprised by how well it works.