Have a look at the Findings from the first European Survey on Language Competences : here. This is a very fruitful survey, quite representative considering the method used (53,000 students of about 14/15 years old enrolled in schools in 16 participating educational systems!).

I’m sure you will find interesting data. It’s not given though that you will find your country because not all the EU Members States have participated. Chapter 7 offers a brief summary and discussion of the most significant outcomes. It shows for example that in their first foreing language, for Reading, 28% of students achieve B2, 14% achieve B1, 12% achieve A2 and 32% achieve A1 ((codes from the  The Common European Framework of Reference for Languages).

It also shows that the proportion of students reaching level B for Listening in the first  target language runs from 14% to  91% across  educational systems!