My son started Mathleague when he was in 3rd grade.  Although he was qualified to State in both 3rd and 4th grade, he couldn’t be advanced to National because of low score in NS.  In 5th grade, we introduced him to teacher Jennie’s NS class.  After one session, he improved his average NS score to 350+.  The most important part is that, he learnt a lot of “mathematical rules” to play with numbers and that enhanced his interest in math study.  He finally placed 22nd in National.  Now he is actively participating in AMC8, Mathcounts and is challenging himself in AMC10.