Forty-four schools in some of Wales' most deprived communities will receive the computers under the scheme, originally drawn-up in a power sharing deal between Labour and Plaid in 2007.
A ring-fenced grant of pound;700,000 over the next two years will fund the pilots, including pound;25,000 to train teachers.
At the launch in Newport, Leighton Andrews, the education minister, said up to 1,200 children aged 10 to 11 will benefit from the pilot, which will help improve literacy and numeracy skills as well as supporting digital inclusion.
But Liberal Democrat education spokeswoman Jenny Randerson attacked the timing of the launch as "mind-blowing" and "blatant electioneering", coming in the run-up to the general election.
Ms Randerson also said that modern classrooms, up-to-date resources and satisfied teachers should be the priority for government education spending.
But Mr Andrews said: "Computers have become as essential a part of school life as books, pens and paper.
"Having access to computers provides clear educational benefits, such as offering pupils more creative learning experiences and giving them the opportunity to do projects and research on the internet."
Original paper headline: Free laptops for schools pilot takes off after three years on runway