Worng, wrong, wrong...I have never stated Hispanic kids shouldn't learn English...they absolutely should, and most Hispanics I know, agree with this.
Most **First Wave*** Immigrants have a hard time assimilating...most of their kids, assimilate quickly...that is true for today's immigrants and for yesterday's.
The problem is rather universal among humans. Most of us learn one language well. Some can learn to speak two or more readily, but they are a distinct minority. Some of us are gifted in being able to dicipher what folks with poor English language skills are saying.
The Hispanic people moving up from Latin America face a double-barreled problem. First off, they didn't receive a good education in Spanish. Secondly, their English vocabulary will, in just a few years experience, become far larger than their Spanish vocabulary. In numerous communities this is driving their creation of a creole language we call Spanglish.
That's why I love Reggaeton music from Puerto Rico ~ good beat, quite danceable, and yet, I can understand what they're saying because they use my words!