Staff and governors at Middlecott School, Kirton, have been given 18 months to improve after a damning report from Ofsted inspectors.
The school was rated inadequate in a report published by Ofsted inspectors who accused teachers of setting work that was “either too easy or too difficult”.
As a result, the school is to be put into special measures which means it now faces regular monitoring inspections and headteacher Julia Garwood will have to produce an improvement plan on how she intends to raise standards.
But inspectors did praise Ms Garwood for making an “impressive start” and for “positive changes” at the school since her appointment in April 2013.
She said: “I’m naturally disappointed with the judgement by Ofsted, however I feel it was the right one to make and it gives me even more leverage to make the changes that I’ve started to make since April.
“I was fully aware of what I was getting into when I joined Middlecott School in April and I’m up for the challenge of bringing the school into the Ofsted category of ‘good’.”
The report said: “For some time, inadequate teaching has led to underachievement for all groups of students and teaching is still not strong enough to reverse this trend.
“Teachers do not routinely use the information they have on what students know and can do to set work at the right level of difficulty for individuals.
“As a result, students are often given tasks that are either too easy or too difficult for them and this often leads to a lack of engagement with their learning.
“Lessons are often dominated by teachers talking for too long, with too few opportunities for students to take an active role in their learning.
“As a result, students lose concentration and can go for long periods of time doing little or no work.”
Miss Garwood and chairman of governors Andrew Cogan discussed the report with parents at the school last Thursday when they also outlined an action plan to raise standards.
Changes include a shake-up in the school’s senior leadership team, better systems to measure students’ progress and increased accountability for teachers.
Miss Garwood said: “The school isn’t under threat of closure but we’re on a journey and the result of this Ofsted report is that we’ll arrive at where we want to be more quickly than we expected.”