Waht about: "V loňském roce jsem byl v šesté třídě" ?
Yep, you can say this too, it's same
The pronounciation of "v" is wrong. It is not a name of letter, but a word. The pronounciation should be different in this sentence.
You mean pronunciation where exactly? In the sentence? In a word tile? Male or female voice?
If you complain about the word tile - well, you can expect various strange things when you ask a computer to pronounce just "v".
Vím, že bych se měla ptát u opačného překladu. Ale jde říct i Last year I was in sixth class? Děkuji
"Grade," "form," and "year" usually refer to the "year" of school. "Class" usually refers to a teaching session. For example: "I am in sixth grade." vs. "English is my sixth class, at 3:30 in the afternoon."