What is educationally possible, and at what age, depends on the child's readiness. In some nations, such as Japan, Singapore, or Hungary, children are generally ready for algebra at 7th grade, if not earlier.
In other nations, tests of algebra-readiness reveal that this is not the case. Since there are some states and cities in the US where algebra-readiness is not widespread at 8th grade, the Obama administration has concluded that any Common Core standard must work like a convoy, sailing at the speed of the slowest city.
This decision promotes equality by preventing the rest of the country's children from forging ahead at a pace that for it is perfectly natural and appropriate.