To replenish, take your class on a short walk or a water break. The brain also dehydrates during learning from heat produced by chemical reactions. Allow your students to bring water bottles from home and keep them at their desk. Use movement and music. Incorporate music at all grade levels, even if only as background while they work.
Background music has a calming effect.
Allow students to learn at their own pace. Every student can not learn at the same time, rate or way. Their brain may not be emotionally ready for the assignment. This is especially true in younger males. If you provide a clear explanation of what the student should accomplish and provide adequate time to practice, give your students three tries to get it right.