Police detailed the charges at a news conference on Wednesday, saying the crimes date back more than 10 years and involves more than $1.5 million in school district money.
The arrests of 18 of those people came on Wednesday. The two others had previously been charged in thefts from the school district.
The majority of the people arrested were tied to an alleged selling scheme. Police say they would order equipment through the school district - including school bus tires and batteries - and sell them.
"They were getting it in the front door and selling it out the back door for 100% profit," said Bensalem Public Safety Director Fred Harran.
Police say school vehicles were also given to junk yards - for free - in return for favors.
"People were getting parts for free for all the classic cars they had been working on," Harran said.
On top of that, the school district was billed for those classic car parts, including one for a '66 Chevelle.
Others were accused of being "ghost employees," and getting paid for doing no work at all. Grounds crew foreman Joseph Dyer is accused of clocking in his wife, Shannon, and another employee every day, even though they hadn't shown up for work in at least two years.
"When I went to see if they were working, I couldn't find the people. It was pretty simple," said Dr. David Baugh, the superintendent of Bensalem schools.
Jack Myers, the business manager for the school district, is facing charges for the lack of oversight. His lawyer, Thomas Keny, thinks the charges are unwarranted.
"If he didn't do his job, he should get fired. Whether or not he stole money and took money? It's our position he did not do that," said Keny.
Police say the investigation is not over and more charges could still be coming. Everyone arrested Wednesday is out on bail, and many are scheduled to be back before a judge at the end of March.
School officials said in a statement that they are creating new safeguards to prevent such problems in the future.
About 6,300 students attend schools in Bensalem.