Elementary School MathLeague.org Contest
Mathleague.org sponsors a number of elementary school contests that are held throughout the school year. The contests are structured in such a way that students will find the tests good preparation for other elementary and middle school math contests. Top-scoring students at qualifying meets held throughout the year will be invited to compete at their state's championship in late April or early May, and winners of the state championships will be invited to the national championship in June.
In the last few years, the Texas state contest have been held in Austin and Houston while the Nationals have been held in Houston and College Station. The previous contest dates and rankings can be found here.