Protesting students held a school principal hostage over fears their degrees would be devalued, Chinese police said on Tuesday.
The protests were over a plan to merge a Nanjing college in Jiangsu province with a vocational institute - which are seen as less prestigious.
Some of the students were reportedly injured as police allegedly used batons and pepper spray on them.
Such protests are rare in China where mass movements are controlled.
Danyang city police said in a statement on Tuesday that undergraduates at Nanjing Normal University's Zhongbei College in Jiangsu province had "gathered" from Sunday and detained the 55-year-old principal on campus for more than 30 hours.
Students "shouted verbal abuse and blocked law enforcement", and refused to let him leave even after authorities announced a suspension of the merger plans, the statement added.
Social media users posted photos of police using batons and pepper spray on students, and one female undergrad bleeding from the head, the AFP news agency said.
The police statement said "to uphold campus order... public security organs took necessary measures in accordance with the law to remove the trapped person, and (the injured) were immediately sent to hospital for treatment.
The hashtag "Nanjing Normal University Zhongbei College students injured by violent law enforcement" was reportedly blocked on microblogging platform Weibo by Tuesday afternoon.
But a video on Twitter showed thousands of chanting undergraduates surrounded by officers outside, as police chased after them and dragged individuals out of the crowd.
All six colleges in Jiangsu province have since said that they would suspend any merger plans which were originally announced in March.
The Jiangsu Education Department had said the decision was to comply with a Ministry of Education directive to transform independent colleges into vocational schools.
The decision has led to protests in four other independent colleges in the province in recent days over similar fears, with "some events of physical confrontation" according to the Global Times newspaper.
Independent colleges are co-funded by universities and social organisations or individuals. Students who do not get the required exam scores to enter university can apply to these institutions, where they can still graduate with a university degree - but at higher tuition costs.
These degrees are seen as more prestigious than vocational degrees, and graduates believe they offer them better opportunities in the country's fiercely competitive job market.
China is expected to have a record nine million university graduates this year.