Almost three-quarters of head teachers have said timetabling pressures affect their ability to meet the needs of young people in the later years of high school, according to a government survey.

The Holyrood study asked them to list factors they believe constrain their ability to develop a senior phase that meets the needs of pupils.

Some 74% suggested timetabling was an issue, while 57% of respondents cited the availability of supply teachers.

Constraints on resources available to head teachers were listed by 66% and the inability to find appropriate partners to help deliver the senior phase was mentioned by 48%.

According to the survey, which took place in June, 158 out of 159 respondents answered the question: "What factors constrain your ability to develop a senior phase that meets the needs of all your young people?"

A surveys were sent to 357 head teachers, resulting in a response rate of 44.5%.

Scottish Conservative education spokeswoman Liz Smith, said: "It is very clear from this survey that teacher shortages remain one of the key concerns for head teachers as they try to implement the Curriculum for Excellence and address the issue of subject choice within the senior phase.

"That is exactly why the Scottish Conservatives have challenged John Swinney to use the recent Barnett consequential funding to improve resource allocation and increase teacher numbers."

Iain Gray, Scottish Labour spokesman for education said: "Head teachers have highlighted issues in designing and implementing the senior phase and ensuring continuity of learning as pupils move on to it.

"Resource constraints, shortages of teachers and insufficient support from Government agencies all add up to a headache for head teachers.

"It's time for Mr Swinney to give our schools the resources they need to allow all pupils to succeed."

The survey also found 97% of respondents claimed to be flexible in the number of choices senior pupils have. Autonomy was also found to be high, with 88% of head teachers responding they had the freedom to design the senior phase for pupils.

Education Secretary John Swinney said: "Almost nine out of 10 head teachers say they have the autonomy to determine the senior phase in their school.

"This demonstrates that our focus on empowering schools is working and that schools are making decisions about how best to meet the needs and aspirations of their pupils.

"These results will feed into our independent review of the senior phase to help us better understand how the curriculum is being implemented in schools and identify any areas for improvement."