I have found for me that I learn best with a continuos effort of learn, repeat and review over a broad number of subjects instead of the learn a, then b, then c.
When I practice golf, I do not learn putting, then irons, then driving. I try all three, repeat all three, then review all three. In basketball, I do not learn dribbling, then learn shooting, then learn passing. I try to improve all three.
I believe that having the children learn english, then math, then science, then foreign language would be a mistake. I believe that throw it all at them, repeat it, push forward, go back and review, then throw it at them again, repeat, push , go back and review, etc. is the proper way to go.
That does mean learning a little spanish, chinese, or fill in the blank with subject of your choice, well before english is mastered.
I suspect, you would normally agree with this, but the mexican invasion has made you so mad that you reflexively scratch spanish off the list.