There were no casualties, as the students were able to escape in time.
The school was closed the day following the fire.
A wooden cross and a dictionary of the Bible have among others been burned.
The police arrested a 36-year-old suspect during the night as he was trying to flee.
Unknown perpetrators entered the church without any problem, as the place of worship is open every day.
Investigators said the deliberately set fires left hundreds of thousands of dollars in damage.
Attacks on Christian places of worship multiply across Western Europe.
The alleged perpetrators may have entered the church from the rear.