Done Some questions inside......

[Guren no heya kara]

1) 青春一直線
What does 一直線 mean in this case?
- Devoted to youth?
- Dedicated to youth?
- Youth full ahead?
...?

2) 南海第二中学校
A doubt on 第二.
It means that it's Nankai second middle school, right?

3) 珠算部
Something better for "calculating with abacus club"?

4) コンサル
It's the name of a coffee launge. Every suggestion is accepted
Maybe a French name?

 

[Aarowaim]

Sorry that I don't have an idea of what the first one means exactly, but I can clear up the other questions.
2) Nankai's second middle school. 第 indicates an 'ordinal' number, e.g, 第一, 第二, 第三 = first, second, third.
南海(の)第二(の)中学校

3) Well, it's a club about using abacuses, so I'd say it'd be 'abacus club'. There's not many other reasons you'd have an abacus club, so the first thing that comes to mind is the correct assumption.

4) I'd say that this would be 'consul', a swank name that shows how 'classy' the lounge is (swanky is the term that comes to mind).

 

[Lefance]

I would say "konsaru" means con sal, which means "with salt", literally. It really isn't a good name for a coffee lounge, per se, but it does sound classy, "Con sal".

"Consul" isn't bad either, though.