The first two years at secondary school are being described as the forgotten years in a new report from the Education Review Office.
The result is based on 68 secondary schools reviewed for literacy and numeracy in 2011.
The report found that, in many schools, students were taught a predetermined curriculum in literacy and mathematics that took no account of their individual strengths and needs.
Graham Stoop from ERO says the report shows that, generally, limited information is gathered throughout the year to tell teachers how well their students are achieving and progressing.
Dr Stoop says Years 9 and 10 seem to have become the forgotten years for assessing students' progress and feeding this information into classroom programmes.
"Often schools were just assessing students formally at the start of the year and the often formally at the end of the year, but there wasn't much in the way of ongoing formative assessment - as we call it - throughout the year to give teachers and schools and idea of where to go next."
Very few schools actually set improvement targets for Year 9 and 10 students, with boards of trustees typically in the dark about their achievements, he says.