Mohammad Liaqat carried out the tirade of abuse at Mount Carmel RC High School, Accrington, because he was angry two Muslims students were banned from lessons because they would not shave their beards.
The 34-year-old has been remanded in custody for sentencing in June after being found guilty at the end of a three day trial at Burnley Crown Court.
It's reported the school had asked the boys to shave their beards because they went against the school's uniform policy.
But Liaqat shouted racial abuse at staff saying they should be allowed to keep their facial hair for religious reasons.
After being arrested at Mount Carmel School and told to stay away he instead went to St Oswald's RC Primary School and used inappropriate language with staff there.
The court was told that Liaqat barged into head teacher Jeff Brown when he asked him to leave.
According to the Lancashire Telegraph PC Dave Hall, from the hate crime and cohesion unit, said: "Ultimately, the issue at Mount Carmel was amicably resolved, but Liaqat decided to take it upon himself to stage his own personal protest.
"He racially abused several of the school staff and he kept referring to Mount Carmel as a racist school. He went on a racist tirade towards the white members of staff.
"He made it quite clear he was deeply upset.
"After being arrested, he was released on bail. He decided to vent his fury o St Oswald's Primary.
"He had reason to be there but not to behave in the way he did.
"Liaqat was causing problems, which led to the head teacher asking him to leave the premises. He reacted by racially abusing staff there and assaulting the head.
"What he did was completely unacceptable. Whatever his motives, we cannot accept this kind of behaviour."