Some schools practice the concept of &quot;mixed age groups&quot; where each class is composed of 3 different ages in equal proportion. For instance my 5-yo son has 3-yo&#x27;s and 4-yo&#x27;s in his class.<p>Thing is, it&#x27;s a constant battle for the school with parents who always want their kids to with same-age kids or older-ones, never smaller ones. Everyone thinks their kid&#x27;s development will be &quot;held back&quot; because of the younger children in the class. Telling them about how older kids also learn from playing or working with younger kids is a hard sell, when all parents think today is academic progress.