Oakwood School at Bicton, near Shrewsbury, was visited in December and was found to have failed a number standards.
Run by Cambian Education, the school caters for children aged between five and 16 who have either an education, health and care plan, or a statement of special educational needs.
Led by inspector Jonathan Keay, the team carried out an emergency unannounced visit.
They found that pupils at the school did not make good progress in their learning due to teachers not implementing plans and schemes of work.
They were also failing to ensure that when a child is away from the school that on their return they make up any work missed. "As a result, there are gaps in some pupils' learning that are not being addressed effectively," said Mr Keay.
"Learning is not challenging enough to ensure pupils make good progress or have sufficient interest in their work. Teachers' planning does not always follow a logical sequence. Teachers do not take sufficient account of pupils' prior learning when planning and delivering lessons. Some teachers' expectations of what pupils can achieve are not high enough. Too often, there is insufficient challenge for pupils."
The inspectors also found that safeguarding policies at the school were not effective. "Staff do not always manage referrals to outside agencies effectively," said Mr Keay. "Leaders and staff do not actively promote pupils' well-being."
But inspectors did recognise that the leaders of the school, which employed a new headteacher in October, were aware of all the shortfalls and that they promoted the pupils' spiritual, moral, social and cultural development effectively. They also found that the school had a rigorous anti-bullying policy and that bullying was rare.
The school, where fees cost more than £20,000 a year, now has to improve in a number of areas. Inspectors have said that the welfare, health and safety of pupils needs to improve as does the quality of leadership in and management of the school.
They have also said that the quality of education provided needs to be improved.
Jeremy Wiles, Cambian Group business development director said: “We recognise that the school currently has areas where it requires improvement. With the appointment of new leadership, and a clear plan we expect to quickly address these concerns and return the school to a standard we would expect”