Principals want the 100 per cent transition policy reversed.
Some students do not merit admission and the policy has led to a rise of indiscipline cases in schools, they said.
The school heads said students who want to pursue vocational training in technical colleges should be allowed to do so.
They said students who cannot read and write are enrolling in Form 1 and are unable to grasp secondary school concepts.
Kenya Secondary School Heads Association secretary Willie Kuria on Wednesday said some students with low marks were reluctant to join secondary schools but have been compelled to do so.
"These students cannot be disciplined, they cannot understand what is being taught. They don't know even what is being said. We cannot rule out the issue of indiscipline because students are [not] in school by choice," he said.
Implementation of the 100 per cent transition from primary to secondary school is in its first year.
Ninety-two per cent of last year’s KCPE candidates have joined secondary schools, resulting in congestion. The number of learners in secondary schools has increased from 2.6 million to 2.8 million.
Principals have cautioned the government to anticipate the effects of the policy in four years.
KSSHA chairman Indimuli Kahi said, "In four years when these students will sit the KCSE exam. You will see results of those who were forced to go to high school when they had not prepared for it."
The principals said they have started experiencing unease and discomfort in schools, which could lead to recurring strikes.
"I wish the policy was adjusted to 100 per cent transition to the next level of learning. The government is spending money on vocational institutions; it clearly shows that after Standard 8, one can join TVET. I think that is what we should have done," Kahi said.
