The Herald understands the woman was stopped after police noticed her bus drifting over the centreline.
Police said the bus was stopped on the outskirts of Cambridge - between there and Ohaupo - sometime before 11am.
Another driver came and dropped the children off at school.
Her result was one of many to shock police recently.
Another woman stopped on State Highway 3 on her way to work in Waitomo yesterday returned a reading of 738mgs while a man stopped on SH1 returned a result of 440mgs.
"That same morning a man was stopped travelling at 137km/h in the 70km/h speed restricted zone outside Whitikahu School. That driver has since had his license suspended.
"Yesterday's incidents follow a mother being stopped while picking up her seven-year-old child up from a Dinsdale Hamilton primary school last Tuesday afternoon. When breath tested the 33-year-old woman returned a breath alcohol result of 805mgs - at 3.15pm."
Mrs Grace said last week's incident followed one on August 6 when a 35-year-old woman travelling with her 12-year-old son was stopped on Rostrevor St, Hamilton, as she drove to a shop.
"When this mother underwent an evidential breath test back at the station she returned a result of 1097mgs, a shocking result and was charged with excess breath alcohol, endangering a child and had her license suspended for 28 days.
"These high alcohol readings and excessive speeds have no place around schools or around children. Therefore I will be ensuring our staff do their part by breath testing every driver we interact with. You can do your part by making sure the people you travel with don't endanger themselves or others on our roads."
Kim Shannon, Ministry of Education's head of education infrastructure, said she was "extremely" concerned that a bus driver had been drinking and was over the drink drive limit.
"This bus service is owned and operated by the school, and isn't a Ministry contracted service. But we contacted the school as soon as we became aware of what happened. They have told us that a replacement driver is now on this service. They fully recognise the serious nature of this incident and like us, they know that the safety and wellbeing of their children is paramount," she said.
