I'm not sure how it is in the Netherlands, but in the US the schools do not decide which computers or systems to use.
The individual school districts come under the individual 'State" School Boards ... there are corporation sellers and lobbyists that petitions and sells their products to the main buyers for the school districts.
Microsoft, hence, Windows is the main OS pre-installed,in the computers, that are bought by the school board buyers. Microsoft does have a marketing plan.
Since most of Linux / Open Source doesn't have salesmen or a marketing plan ... it's hard to get your foot in the door with the right people.
So, if you know the right people, the buyers for the state run school boards ... then, you might have a chance.
You would also, have to be 'representing' a major Linux OS
and computer manufacturer.
I think the only Linux/Unix systems that might have a marketing plan are Novell, Red Hat and Ubuntu (there might a a couple more)
But, they are marketing primarily the Operating Systems and not computers with Linux pre-installed to corporations.
Most of the big schools (and all of the smaller schools) are prey to Microsoft and the lobbyists as to which and what kind of computers they have.
In the community colleges, technical colleges and and universities that offer IT or computer courses ... if you use your own laptop ... they are usually MS Windows
required.
Boy ... that sounds 'grim' ... and we expect our kids to get a proper education?
I was talking, on-line with the son of an ex-girlfriend recently. He is attending the Devry Technical College in Texas.
He said that most of his computer courses are in Windows Vista (he personally has W-7) but that he took a separate IT class for 'no credit' in Unix-based systems.
(This is funny) That in the class they originally stated by learning Fedora 9 ... but have recently
advanced to using Ubuntu 9.04
He didn't even know there were 'so many' Linux OSs ... I introduced him to DistroWatch.com