I have taught in co-ed schools, but I am currently teaching in an all-boys' comprehensive school in the North of England. This often raises eyebrows, especially with the general consensus being that boys don't really do languages. Our experience is that boys do languages, and can do them well. We may have an advantage having no girls, as it can't be seen as a "girly" subject, and boys can't hide behind the girls. I'd like to share some of the observations I've made in the past few years. Yes, there will be some generalisations, but I hope some of this might be useful.
Keep it short, keep it clear, keep it simple
I find boys less tolerant of waffle - eyes glaze over much quicker. They want to learn what they need to, and they want to get on. I think my instructions have become much clearer in the time I have been here. They also value step-by-step instructions, and will switch off if things seem too convoluted. Don't make "busy" worksheets - if it's not clear, they will simply not use it, however, if they can see the steps clearly, they will generally respond.
Give them the nuts and bolts
Boys generally like to see how things work, how they fit together. Give them the tools and understanding for this, and you have your slam dunk for progress.
Getting them speaking
Boys are generally willing to speak if they have the confidence. I find teaching phonics very important. They feel they can "have a go" - I have the important sounds very prominently on my learning wall, and they use it a lot. The boys like to interact, and each table has a "speaking mat" on it, which emphasises phrases they can use with each other. They enjoy learning how to agree and disagree, which also plays into their sense of humour. By gradually introducing the different elements of group talk, I find you can model with them how to communicate with others. Teaching them simple questions, such as "and you?", and giving one boy the job of keeping everyone involved allows them to learn basic conversation skills for any language.
Humour and imagination
Boys are often very sharp, and they love using humour. I sometimes use it when presenting vocabulary because it can grab their attention, and games such as making up nonsense sentences allows them to express themselves. This can be used to your advantage, but be careful. Make sure that your classroom expectations have set clear boundaries. Boys together can be also incredibly silly. Also be aware that the class entertainer is often hiding some deep insecurities, and he needs to find ways to have a sense of achievement away from this persona which he has adopted.
The boys have great imagination, and will use it, especially if it allows them to do something a bit gory or disgusting. They will also get involved in acting, role-play and they enjoy making videos, even using puppets. It brings some boys out of themselves, especially if they can take on another persona.
Points mean prizes - how to get them to develop their ideas
Sadly, I never get any work anymore where the title is underlined in sparkly gel pen, and one other battle I have is getting boys to develop their ideas. This requires several approaches - you need to develop their concept of how they can expand their ideas, however, they also need something very simple to hook them. Boys are often very competitive, so any way of getting boys to score points works wonders. I get them to score points for certain linguistic points - the more ambitious aspects score more points. They love being able to see the points accumulate. This works for speaking and writing.
This is one way - I teach German, but I'm sure you can adapt:
1 point - und, denn, aber (simple connectives), sentences in the first person
2 points - connectives which require the verb to come next (jedoch - however etc), frequency words and adverbs of time, sentences with "we" or "they"
3 points - connectives which send the verb to the end of the clause, different tenses, adjectives with correct endings, verbs in the he/she forms, questions
The importance of re-drafting
I have many pupils who rush work, and hate checking their work. That is where re-drafting becomes so important. Devoting some class time to calm reflection on their work has a big impact. It also models good study skills. Make sure the improvements are clearly targeted, and can be done in the time you've allowed.
Catching the boys who are losing heart
It's important to catch boys before they give up. The re-drafting time in class gives me an opportunity to spend a few minutes with those boys, and show them that often there is an easy way to dig themselves out of a hole. If you catch them as they wobble, they can respond well. Get feedback - a quick questionaire at the end of a half-term allows me to tweak my planning, and I'm sometimes surprised by the things the boys say they want more practice with. I have a weekly "catch-up" session, which is for boys who have been absent, boys whose homework was not up to standard, or boys who need something going over.