Builth Wells High School had eight minutes to question Maj Peake -  who became the first Briton to walk in space on 15 January.
They used amateur "ham" radio equipment to communicate with ISS as it travelled 215 miles (346km) above Wales.
Signing off, Maj Tim told the students: "It's been great talking to you."
Eight of the school's pupils asked questions on Saturday, with two more from Gwernyfed High School near Brecon also taking part.
Gwen Davies, head girl in Year 13 at Builth Wells, asked Maj Peake - who watched England's Six Nations rugby match against Scotland from space - whether the signal for the broadcast was any good.
He replied: "I really enjoyed watching the rugby up here and I was very grateful to get it sent up,  but I assure you it probably wasn't a better picture than the one you got on Earth."
Pupils also asked scientific questions, such as one about the materials the mission is testing to see how they weather in the the space environment.
Maj Peake said he exercises for two hours a day in space to keep fit.
He also explained it could take up to two years before the density of his bones is back to normal after he returns home.
More than 200 people attended the event at the school.
On Tuesday, Maj Peake sent Wales a St David's Day message.
He was previously questioned by Rhys Maguire-Stokes, eight, of Blaenymaes Primary School, in Swansea, via Twitter.
Astronaut Tim Peake has been quizzed by Powys high school pupils via a live link with the International Space Station (ISS).