"Having a librarian," the principal said, "just helps to support what's going on in the classroom, with teachers. I just felt like it was a necessity. It would be remiss not to have a library."
Robinson is bucking a trend. In 1991, there were 176 certified librarians in city schools. Now there are 11 - for 218 schools.
Studies have shown that students who have access to a school library and librarian - particularly students who live in poverty and students of color - achieve more.
"And somehow," Masterman School librarian Bernadette Kearney said, "we struggle to get recognized as relevant to schools."
Increasingly in Philadelphia, school libraries are regarded as a frill, and librarians even more so.
Debra Kachel, who teaches in the School Library and Information Technologies Program at Mansfield University, said that 10 percent of all school library jobs have been lost in the last four years.
"We're seeing cuts everywhere," said Kachel, who researches statewide school library issues. "But it's the school districts that have the neediest learners that are hit the hardest."
Still, most suburban districts wouldn't dream of shedding librarians wholesale.
"The wealthy schools have great programs, librarians teaching kids, coaching them, developing a habit of reading with those kids," Kachel said. "Librarians are teaching critical thinking skills, how to search the Internet, how to be safe on the Internet. If you invest in a school librarian, you invest in improving student learning."
Philadelphia Superintendent William R. Hite Jr. says he's a fan of school libraries. "We should have as many libraries as we can possibly have," he said. "And we're providing principals with the ability to make that decision."
But given minuscule discretionary budgets, Philadelphia principals are often closing school libraries or leaving them unstaffed - just rooms with books and aging, uncurated collections. The lucky ones have volunteers or community partnerships to keep libraries open, but still lack full-time professionals to curate and teach.
"Who knows if we'll ever have 200 librarians again?" Hite asked. "We have to think about how do we provide children with the opportunity to access information using the digital tools and partnerships available to us."
Kearney, the Masterman librarian, would argue that's not enough.
At her school, regarded as the best public school in the state, Kearney has hung on, but narrowly. She lost her library job to budget cuts in 2013, but was restored two months later when a donor stepped forward to fund the job.
Her position was threatened again this year, but former principal Marjorie Neff saved Kearney by classifying her as a teacher, and assigning her 18 classes a week. The schedule leaves Kearney feeling as if she doesn't have enough time to do all the things she once did - fully serve students' and teachers' needs, plan activities, apply for grants, update the library website - but a group of parent and high school volunteers helps keep things running.
To Neff, now retired from her principal's job and a member of the School Reform Commission, the loss of the school librarian is unthinkable. At both schools where she served as principal, Neff said, "the library was the center of the school program. I just don't see a library as an extra."
Every inch of Masterman's library is used, and every moment of Kearney's time is occupied.
On a recent day, she was in perpetual motion: teaching classes, working with students struggling with research methods, helping young people meeting to form a Reading Olympics team. Kearney gave up her lunch and prep periods, as she does most days, to maximize students' time in the library.
She knows who likes to read graphic novels and who's a fan of biographies. She tailors her collection to teachers' projects, and she is forever coming up with reasons - Harry Potter quizzo at lunchtime, anyone? - to make the library not just a place to study, but the heart of the school.
"Schools are about building thinkers," Kearney said, "and the library is the thinking place."
At Crossan Elementary in the Northeast, Lynne Millard is like most principals in the city: wishing she had a librarian, but unable to find the funds to pay for one.
"When funds dwindled, the position disappeared," said Millard, who has been Crossan's principal for six years. "The books are still there, but we don't use them."
Crossan students tend to perform better in math than they do in reading, and Millard thinks a librarian could help work on literacy skills, but there's no money for one.
"I'd love a library," Millard said, "but that is just so far from my reality right now."
Some states require school libraries; Pennsylvania is not one of them. Kachel has reached out to legislators about potentially having such a requirement in the commonwealth, to no avail.
"We are soon going to have an entire generation of school students who have gone kindergarten through high school and who have not known what a school library is, and have not had access to those resources to learn," Kachel said. "I find that unconscionable."