With years of games such as Super Mario on the prohibited list, she says students weren't expecting the Nintendo welcome.
"They've been using it at home playing games, so at first they were surprised they can use it at school," Okubo said.
Still early in a one-year free trial period, vice principal Junko Tatsumi says results so far have been encouraging in Japan's long struggle with English language education.
"The students are really concentrating and have fun in gaining skills such as spelling," she said. "Our school policy is English education should be fun."
Japan has around 15,000 middle and high schools and in 2000 launched reforms to create a more "relaxed" environment aimed at fostering creativity and reducing rote learning.
Nintendo was not envisioned as part of that plan and remains a rare find at most Japanese schools, while an OECD educational survey of 57 nations last December showed Japanese 15-year-olds falling in rankings for science, mathematics and reading.
Japan's education ministry leaves decisions on teaching tools to schools, but if up to first-year student Kanako Takahashi, the DS would be a no-brainer.
"It's fun and helps me remember English," says the 13-year old. "There's also math software that would be great to try."
So far, it's only English at the all-girls junior high, but at selected schools from Tokyo to Nintendo's home of Kyoto, the DS console and stylus are employed in math and Japanese classes.
Nintendo says the number of schools with consoles is still small, but the DS's touch screen and mix of advanced and easy-to-learn games, including 200 licensed education titles, has been a cash cow as more women and older consumers try it.
Global DS sales since launching in 2004 exceed 70 million units, but even with ubiquity, faculty acceptance of Nintendo use at the over 100-year-old Tokyo Joshi is not universal.
"I had been using it myself, so I wasn't uncomfortable, but other teachers who had never used the DS were a little bit worried because it's a game," said Okubo.
But the school's vice principal says stylus lines are clear.
"No unessential item is allowed at school," said Tatsumi, adding playing cards and mobile phones to those off-limits. "When English class ends, students cannot play DS games outside and all consoles and software are collected."