Oh they do, depending on how you define &quot;mature&quot;.  The primary difference isn&#x27;t really an age thing though.  Typically, girls in classrooms are perfectly happy to sit still and listen.  Boys, not so much.  Obviously, this isn&#x27;t binary, it&#x27;s a continuum.  But oh boy does it skew heavily.<p>When we&#x27;re talking about a general rule for the masses, I don&#x27;t think different cutoffs would be that helpful past 4-years old.  It would be more beneficial to split them up and teach them differently.  That said, it&#x27;s far more important for parents to make these decisions for their own child.  Sometimes they&#x27;re ready, sometimes they aren&#x27;t.  But there&#x27;s a lot of growth that can happen when we aren&#x27;t quite ready for something or when we don&#x27;t think they are.  Everyone is far too afraid of failure, or barring failure, afraid of difficulty.  Let them try.  They might surprise you.  If they struggle, help them along.  The trouble is, there are a lot of kids who struggle and simply can&#x27;t or won&#x27;t get the help they need to grow through it.