A crew from Papworth was called to a fire in the open off the A1198 Papworth Bypass, between the Yelling roundabout and Summers Hill Estate.
A large heap of school exercise books and revision books had been set on fire and left unattended.
Firefighters extinguished it using hose reels by 10.30pm.
The cause of the fire is believed to be deliberate. Anyone with information should contact the police on 101 or the independent charity Crimestoppers anonymously on 0800 555111.
Martin Ward, watch commander at Papworth, said: “We understand it can be very exciting for many young people to have already finished school and a relief for some who have now completed their exams, however, we would urge students not to set fire to their books – especially in public places.
“By starting a fire you are putting not only your own life, but the lives of others and nearby properties around you in danger. If you don’t want your schoolbooks then put them in the recycling or return them to your school, but please do not start fires.”