Understanding a colloquial sentence and meaning of やっぱ

Question

The kids are discussing whether they want a male or female trainee teacher. One of them runs in from the playground and says:

「やっぱ男じゃねぇとな」

I assume this is a colloquial form of

「やっぱり男じゃないと言ったな」
As expected, I said that it's not a man.

I think my translation must be wrong because afterwards we have:

「...上品で清楚なレディだとうれしい」
「いやいやいやン。ああ神様、どうか男の人が来ますように」
...I'll be happy if it's an elegant well groomed lady
No way! Ah, please God, let it be a man.

which suggests that they still don't know the identity of the teacher.

How should I understand やっぱ男じゃねぇとな?

Answer 1

It's probably やっぱり男じゃないと（できない）な or やっぱり男じゃないと（だめだ）な.

Probably referring to the character wanting a male teacher because of some internal reason (perhaps his image of teachers are male or there is something else previous that gives that impression that he prefers male teacher over female)

Answer 2

Think of it as the very casual "Honestly, if it ain't a man, well...." where "Honestly" is "やっぱ(り)" and "well" is "な".

The forms "-ないとならない", "-ないといけない", or "-ないとだめ" are so usual that in spoken language it's common to drop what comes after the "と". Most likely here, it's "だめ", expressing the locutor's feelings.

You can see the parallel in the next sentence: "... レディだとうれしい", which quite literally means "if it's a (...) lady, I'm happy". Here, the parallel is "Xだと || feeling": "If it's X || I feel happy"