There will be a time when your kids will do a lot on computers at school. It is just the way things are going. Like switching from slates to large black boards.
We greatly monitor our kids computer time and my 12yo does have his own laptop. He uses it tons for school and not so much for games when school is in session. He has to earn his time by doing chores.
My parents take my kids on trips a lot and sometimes, when they have missed school because of it, they have done powerpoint reports for school. That has helped them manipulate the computer.
It is a whole different learning environment between my 12 and 9yo even though they go to the same school. Computers were hardly used with my 12yo when he was in elementary and now my 9yo is using them at school for everything in elementary.
It is not poison. Relax a bit.