Here are other math-related activities you should know about.
AMC 8:
https://www.maa.org/math-competitions/amc-8Mathcounts:
https://www.mathcounts.org/Wolfram Middle-School Summer Camp:
https://education.wolfram.com/middle-school-campArt of Problem Solving (AOPS):
https://artofproblemsolving.com/companyThe Exeter Math Club Competition(EMCC):
https://exetermathclub.com/Math Kangaroo:
https://mathkangaroo.org/mks/