CLIL - can it work in practice?

I believe that most teachers would agree with the statement that teaching English through content can bring a lot benefits. It changes classroom dynamics by making the learners more involved in the processes of knowledge construction instead of 'putting information in the heads of learners'. However there are still doubts about how it should be implemented on a daily basis. I think this might be a challenge for the teachers, the students and the school administration. On the other hand, it should be one of modern schools' priority to aim at introducing bilingual classes when the number of students attending schools is decreasing due to the demographics. A few years ago I had an experience of preparing a chemistry lesson in English in my school and I must admit that it involved a  lot of preparation both on my side and my colleague - the chemistry teacher. First, I needed to  become an expert in the material covered by the lesson and then I had to design every minute of the lesson to be sure that both content and language are learnt. The lesson was observed by a few teachers and the headmistress who really liked the idea and suggested continuation of such events.
And I think that using the word 'event' to describe this lesson is the key to explain why it is so hard to put CLIL into practice. In most Polish schools such lessons will remain big events, very hard if not impossible to organize. There a few reasons for this state. One of them is surely the attitude of some Polish teachers which is, to paraphrase the saying 'my home is my castle', - 'my class is my castle' - we do not like to share ideas, we do not like to cooperate. As a leader of teacher training at my school I wanted to organize open classes the aim of which would be i. a. to learn how CLIL could be introduced but none of my colleagues agreed to let other people in their classes explaining that they would feel too stressed. I think that one of the solutions to the problem would be introducing more flexible organisation of classes, supporting teachers in preparing cross-curriculars project not only by telling them do work this way but by giving tools and proper training. It is of course possible to introduce CLIL without this help but it will remain a very demanding task.