Forty-nine year old Steven Warren Wesley Sr. was taken into custody on Friday.
The Westtown-East Goshen Regional Police Department received a report that the assault happened inside Stetson Middle School located in the 1000 block of Wilmington Pike.
The 28-year-old victim works for the West Chester Area School District as well and told police she was attacked Thursday night in a small office inside the school.
At the time of this incident the Stetson Middle School was closed and no students were inside the building.
The victim was treated and released from the Chester County Hospital.
Police arrested and charged Wesley with Rape and Sexual Assault among other charges. His bail was at $500,000.
Wesley has worked for the school district for more than 17 years.