The former chief inspector of schools, Chris Woodhead, has estimated that there are around 15,000 incompetent teachers in Britain. The former Government education adviser Sir Cyril Taylor puts the figure at 17,000. And yet just 18 teachers have been struck off for incompetence by the General Teaching Council (GTC) in 40 years.

The implications are depressing. It means that hundreds of thousands of children are receiving a substandard education because poor teachers are not being removed from the schools system.

There are two forces at work here. The teaching unions are protecting inadequate teachers and head teachers are shuffling them on to different schools to avoid the hassle that would be involved in referring underperforming staff to the GTC.

Both practices need to end. Just as we would not accept incompetent doctors or incompetent airline pilots, we should not accept incompetent teachers. Their function – the education of our children – is no less important. The Government's decision to disband the manifestly broken GTC is a necessary first step to reform. But the unions also need to be made to understand that it does the majority of the competent members of their profession no favours to fight for those teachers who are simply not up to the job. If a teacher cannot control a classroom, they should not be in that classroom.

And, as the new head of the House of Commons education committee, Graham Stuart, argues today in an interview with this newspaper, head teachers need to be told that they cannot continue these games of pass the rotten parcel. If a teacher cannot control a classroom in one school, there is no good reason to imagine that they will be able to do so in another.

Despite the claims of the teaching unions, this is not about undermining the teaching profession and their rightful legal protections. Those who educate children should be especially valued by society. The prestige of the profession should be considerably higher. And teachers found to be incompetent should be given an opportunity to retrain, rather than just expelled.

But this lazy practice of turning a blind eye to incompetent teaching cannot be permitted to continue. It is a betrayal of competent teachers and – still more scandalous – the children whose futures can be made or destroyed by the quality of the education they receive.