First, I think we should try to avoid saying 'oh', because that's a letter, not a number. However, we should bear in mind that 'oh' is commonly used as a number. I think many of us probably start 'oh seven ...' when we give our mobile phone number. 'Oh' is used in telling the time with the 24 clock too eg 16:05 is said as 'sixteen oh five'. 'James Bond double oh seven' is another example. But although it's acceptable in conversation, 'oh' shouldn't be used for the number 0 in a maths classroom.
I use the word zero quite often, for example I tell my students to make a quadratic equation 'equal to zero'. I'd say 50 as 'five to the power of zero', and so on. I wouldn't say nought in these cases, though there's nothing wrong with saying nought.
I do sometimes use the word nought instead of zero. For example I would say the number 0.64 as 'nought point six four'.
Although there is a perception that zero is the 'best' way to say the number 0, I'm convinced that the word nought is still widely used in the UK, particularly in numbers with decimals. I did a Twitter poll to check what maths teachers say. Twitter polls are of limited use because they provide no information about who has responded (ie what continent they are from), but the results are still of interest:
The large number of responses for 'nought point five' confirmed that the word 'nought' is still widely used, at least in the UK. A few tweets from North America suggested that it's rarely used there.
If you're wondering about the spelling of the word nought, this extract from Wikipedia 'Names for the number 0 in English' might be of interest:
The words "nought" and "naught" are spelling variants... There is a distinction in British English between the two, but it is not one that is universally recognized. This distinction is that "nought" is primarily used in a literal arithmetic sense, where the number 0 is straightforwardly meant, whereas "naught" is used in poetical and rhetorical senses, where "nothing" could equally well be substituted... Whilst British English makes this distinction, in United States English, the spelling "naught" is preferred for both the literal and rhetorical/poetic senses.In summary, I think it's fine to use the words zero and nought interchangeably in the maths classroom, as long as your students know what you're referring to. Do you agree?
♫ You say zero, I say nought
Let's call the whole thing off ♫
Further reading: BBC 4 In Our Time Debate: Zero