Yes, kids need a break too. Whether it is in the school or during the study hours at home, they too deserve a break. Many studies indicate that kids will learn at a better pace when they are offered frequent breaks.
So, forcing your kid to study for long stretches isn't a wise decision both in the school and at home. Also, kids tend to process the information one bit at a time and it becomes very difficult if you force your kid to study too much without a break.
And then a break would surely enhance the focus of your child. After a break, your kid tends to work with a refreshed mind and this helps him process more information and absorb it well.
Apart from all these things, sending your kid out into the natural light is also important. Many studies say that sunlight stimulates the human biological clock.
And yes, the immunity of your kid needs sunlight regularly. Keeping kids indoors for the whole day isn't a wise thing in the growing age.
Also, your kid can de-stress during every break. Without beaks, the stress would buildup and cause frustration in kids. They would hate studies if you never allow them to take short breaks.