I wonder with all of these observations of learner behavior if teachers read up on language acquisition in general. While there are many studies of acquisition both of first language and second and more language, we can look at the history of our own language to see how people acquire a second language imperfectly. Thousands of Vikings speaking a closely related language, Old Norse, settled in England. Many of the forms in modern English so derided, ridiculed, and snubbed by the middle class in this country derive from those early forms in Northern English, i.e. northern England. A good deal of Northern English comes from the same sort of interaction between Old English and Old Norse speakers that we see in the U.S. today between English speakers and Spanish speakers. Just yesterday, I heard a comedian do a good imitation of Chicano speech aka Spanglish. I have heard Anglos who do not speak Spanish speaking English with a Mexican accent, quite normal when you attend a school along the border with a heavy Hispanic representation in the student body.
So why should acquisition be any different in our classrooms? The reason is that we still maintain the unnatural expectations of academic work rather than natural acquisition. We can hear major public figures speaking English with marked influence from another language, yet only bigots reject their thoughts b/c they are not expressed in indigenous English. My Spanish will never be native-like but I participate lustily in conversations in Spanish. The “hay” “tener” confusion could very well be a routine misinterpretation. If so, we may see students graduating with conversational and reading ability in Spanish with some glitches. While this particular confusion is major, there are many less egregious “errors” we just have to get used to (I use the work “error” b/c it comes about without the speaker’s awareness; a “mistake” is when the speaker knows the indigenous form but just misspeaks).
For a nice review of Northern English (Northumberland, Yorkshire, etc.) see Histories of English by Trudgill and Watts, the chapter ‘North of Watford Gap’, a cultural history of Northern English (from 1700); it’s more on attitudes than on the actual forms found in this variety of English. There’s plenty of material on the latter if you are interested; if you are, contact me for bibliographical references.
For other languages, see John McWhorter’s Language Interrupted; heavy going but worth at least perusing for how many world languages are shadows of their former selves after being acquired by masses of people as a second language: Persian, Arabic, Mandarin, Indonesian, and many more, not to mention Latin, now known as French, Spanish, Italian, Rumanian, Portuguese, Catalan, Occitan, Romansh, Sardinian, and so on.