He has been bailed under next month pending further inquiries.
Police were alerted to the incident after receiving a number of calls from worried parents.
One mother, whose 12-year-old son was jabbed with the diabetes pen, which acts as a blood-sugar testing device, said: “It was worrying and shocking to be told what had happened.
“I had to sit in the hospital for four hours while my son had a blood test and a hepatitis B injection.
“When we came out the waiting room was full of other students.”
Carl Williams, headteacher at the school, called the incident “deeply concerning” and added: “As soon as we were alerted to it, we contacted parents of the children affected and spoke to the local police.
“We are also working closely with public health experts .
“While the risk of infection is low or negligible, children affected have been given a vaccination for hepatitis B.”
Steve Perry, Low Hill Neighbourhood Police co-ordinator, said: “We received three reports on June 2 from parents saying their children had been jabbed with a diabetes finger-prick pen by a fellow pupil while at Moreton Community School.
“Officers have identified as least 20 children it’s believed were jabbed with the pen.
“It has a needle ‘nib’ just 3mm in length so none of the children are seriously hurt and public health officials have advised that the chance of infection is negligible.
“However the pupils have been advised to have hepatitis injections as a precaution.
“An 11-year-old boy was arrested from his home address in Low Hill on Tuesday and having been questioned by police has been bailed till a date July pending further enquiries.”
All pupils involved in the incident were told to report to a local Accident and Emergency for a free hepatitis B vaccination.
Ros Jervis, director of public health for Wolverhampton Council, said: “I am reassured that all agencies have responded very quickly to what is a very serious situation.”
Moreton Community School caters for over 700 boys and girls aged between 11 and 18 and had suffered a drop from “outstanding” to “requires improvement” following an Ofsted inspection in 2012.
The school was criticised for “inconsistent” teaching but pupil behaviour was described as “good”.
Boy, 11, arrested soon after twenty schoolchildren stabbed by needle
