"I condemn the use of tear-gas on children and the involvement of children in the riot," Police Inspector General Samwel Arachi said in a statement.
"The officers leading the operation on the ground will be suspended immediately," he asserted.
Anti-riot police fired tear gas canisters at students of Langata primary school in Nairobi who were protesting the sale of their playground to a private developer.
Returning to schools after a two-week strike by teachers, the students were dumfounded to see a wall cutting through their playground.
Three children who were choked by the tear-gas fainted and were rushed to Langata Prison Dispensary where they were treated and discharged.
"We are going to launch an investigation into the event from where stern action against the organizers of the demonstrations will be taken," Arachi said.
"We are also going to investigate and bring to book all the officers who lodged tear gas canisters at the children," he added.
Opposition leader Raila Amollo Odinga, a former prime minister, slammed the police action.
"This is brutally beyond words and greed beyond description, it is difficult to believe that police can actually deploy against primary school children and lobby tear gas at them to defend the land grabber," he said in a statement.
"This image of a nation determined to steal forcefully from its own children cannot be what we aspire to, it cannot be the legacy we want to bequeath the children," Odinga insisted.
"Somebody must be held accountable for this primitive and shameful action," he added.