Each country’s government determines the dates and duration of school holidays—and these are completely independent of school holidays in other countries (there are huge differences even among neighbouring countries within the European Union). The following map shows the total length (in weeks) of school holidays (in primary education) in most European countries.
The following map shows the total length of school holidays by country. Compiling the data wasn’t easy, so, please, take the figures with a pinch of salt (there may be errors). If a range is given instead of a single figure, the duration varies among different regions or different school years within one country.
P.S. I wasn’t able to find data for some countries. If you know where to find them (or if you find any error in the figures), please, let me know in the comments.