Actually that isn't unique to the school you worked at, it's a philosophical feature of the education system. I wasn't allowed to use a computer until I was perhaps 11 years old, and then only sparingly. I don't think it affected my later abilities, and I was incredibly excited once I got the chance to code at home!

I think this came about partly as an extension of Steiner's views on television as something that stunts imagination and creativity. The first 7 years of the education have a very strong focus on mental imagery, and there is probably a belief that viewing concrete depictions of concepts on a computer is harmful.

I happen to believe that a computer can allow increased exploration of the imagination when used for creative tasks, but in the 90's schools were mostly using them for looking at Encarta and so on. That's exactly what Steiner schools want to avoid for their younger children.