A project to spruce up dreary hallways at inner city schools offers a simple premise: Bright walls make for brighter students.

Publicolor, a 10-year-old program where students are permitted to paint over the industrial shades of their schools’ interiors, is credited by school officials with lowering dropout rates, decreasing discipline problems and increasing attendance. The program has already redecorated 71 schools in blighted city neighborhoods.

“This is probably the best kept secret in New York City,” the P.S. 69 principal Alan Cohen, whose Bronx school was painted earlier this year, said. “I love Publicolor. It has changed my school from the inside out.”

Students feel the same way. On Thursday, 14-year-old Pedro Rodriguez was busy splashing oriole orange and apple green paints on the walls. The old colors, he said, “sometimes would make you feel down.”

Not anymore.

“My school stands out,” Pedro said. “I feel more confident. I like doing work now and I actually like being inside the school building.”

The dull colors on tile walls at P.S. 34 gave way to shimmering lime, teal blast, yellow flash, tangerine zing, and blue wave. The bright shades contrasted with the tall grayish buildings in the surrounding neighborhood, where Pedro was mugged last week as he walked home from painting the school.

“It’s not a very good environment. It’s like a violent place when it gets dark,” said the teen, who still had a lump on his head from the attack.