I agree that the net and texting has really caused some issues with teens and spelling. In fact, when my son was in school (graduated last year), he was allowed to use a spell checker on essays in school and encouraged and even demanded to use the net - with its spelling and grammar checking abilities - to write his papers.
I didn't have that luxury. I am old. We were excited when we got electric typewriters in our schools. I had to learn how to write and and spell myself. I had to look things up in real dictionaries and do my research from books, not google searches. That is NOT to say I had a better education than today's kids because they really are learning some amazing stuff. But allowing kids to spell wrong or to take shortcuts isn't helping them at all.
One teacher told me that all my son REALLY needed to know was how to write his name to sign things when I was concerned at how sloppy and misspelled his writing was. Maybe that is all he REALLY had to know to get by on the lowest level but I wanted my son to learn how to form sentences and be able to write things that didn't require an interpreter to understand. He got better as he aged but he never really was encouraged to at school.
Parents have the ultimate responsibility to make sure their kids are learning. That's the bottom line. Teachers really can only do so much and then it's up to the parent to talk to the teachers and their kids and plan out what to do. I had to do that with my youngest son and he ended up doing very well but, for a while, he was coasting and doing the bare minimum if that. And he tested at college level in 7th grade!