"YOU ARE WRONG.
Brazilian Portuguese has a tendency to use EM (in, into) with verbs of movement, especially CHEGAR (arrive), IR (go), VIR (come), as in Latin: in urbem ire (to go into town), or in German (in die Stadt gehen) or to a certain extent, modern English (arrive in Rome) or Italian (vado in discoteca). "
Tendency doesn't make an usage right. Rather, that the SPOKEN language has a certain preference. Trying to force a diacronic view based on Latin won't change the fact that "em" is a colloquial and wrong usage of a preposition for indicating direction. I don't know why you're trying to use German or Italian to try to prove what's WRONG.
"No Brazilian would ever say ''chego a casa'' or ''vou lá a casa''. It's ''eu chego em casa'' or ''eu vou lá em casa''. "
As for "chegar em casa" you might be right when it comes to the SPOKEN language. However, an EDUCATED person would write "chegar à casa" as one can see in an article from the "Folha de São Paulo".
"Racismo deve impedir Obama de chegar à Casa Branca, diz Chomsky"
I say "chegar em casa" because it's common for doing so but will NEVER write like that. As for the example "Chegar em Roma", I would prefer "Chegar a Roma", which is , again, the CORRECT usage and I don't care if people around me say "Chegar em Roma".
I don't believe you say "I ain't got no money" just because people around could use it...
Look what dicionary of verbs says on this (Dicionário Prático de Regência Verbal, C.P Luft, Editora Ática):
''No português brasileiro também ocorre ir em, sobretudo na fala, o que pode ser até sobrevivência da língua arcaica, herança da língua-mãe (latim: 'in urbem ire'): Vou em casa. Foi no centro (no médico, no cinema, etc.). Ver documentação literária em Nascentes (1953: 171-4), Lessa
(81-3, 186-8), Barbadinho (60-2). Escreveu Mário de Andrade (Lessa: 187) em carta a Manuel Bandeira: "Os portugueses dizem ir à cidade. Os brasileiros: na cidade. Eu sou brasileiro".
Again, trying to force a diacronic view of the language doesn't help explaining how the language works NOW.
As for the last example, I don't feel as being PORTUGUESE for saying "Ir à cidade". I say it all the time and don't bother if people will think I'm snobbish.
"2. Modern Brazilian grammars (like Modern Portuguese, by Mario Perini, published by Yale University Press) are fine with this usage, it's a real fact of language, just like Americans say ON THE STREET and not IN THE STREET, Brazilians say CHEGO EM CASA and not CHEGO A CASA. My Portuguese professor never corrected us, and she was using chegar/ir/vir with EM normally, and she has an USP degree. "
A fact of the language can't substitute the normative grammar. Well, at least if one wants to get a decent job and be seen as an educated person.
There's no need for your teacher to correct you but I think she should at least show that "em" is more popular. Having a degree from USP has nothing no do with one's language usage since a godo speaker should be able to use the worst slangs at the same time that he/she can use the most formal language.
"3. Even Portuguese grammarians are fine with this Brazilian usage:
Thanks for the link but I guess we're talking about Brazilian Portuguese, aren't we?
If you want to continue this conversation please make sure if you want to talk about "spoken" or "written" language because it seems you cannot differentiate them.
p.s In case you have been reading the posting on PB and PE you can clearly see that PE and PB are different when comparing the spoken language but quite close when comparing the WRITTEN language.