Angry parents rowed with staff after children as young as 12 were forced to stand in the rain for around 45 minutes whilst their bags were checked to ensure they had a green pen.
In the confusion, some children rang parents and many left the school for the day. The green pens are reportedly used to mark the work of other pupils.
Lisa Corrigan, principal of Park Lane Academy said: “Park Lane Academy is undergoing a transformation that has seen 60% of subject areas show improved results in summer 2018.
"Indeed, maths and science improved by almost 20%. The turnaround is underpinned by helping our students to become more organised and prepared for learning.
“Following equipment checks this morning, students were asked to queue so their heads of year could give them equipment and speak to them regarding being prepared for learning.
"All students were given green pens today to respond to feedback from teachers in their exercise books. Parents received a text message about equipment.
“The school entry procedures have also been amended in order to allow students into school more quickly.
"No children were sent off-site or told they would not be allowed entry into the premises.”
The school indicated to parents in an message that 'morning procedures' would be amended to ensure that they bag checks could be carried out more quickly.
The message said: "Following the slow start to this morning's lessons we will be amending the morning procedures.
"As of tomorrow, different year groups will enter through different doors in order that uniform and equipment is checked more quickly.
"All students will be given a green pen today free of charge, but we ask that you maintain talking to your children about being organised for school."