HERE’S a multiple-choice question: if the federal government penalises states where pupils do badly in school, but lets the states themselves set the pass mark, will the states a) make the tests harder; or b) dumb them down? Historically, the answer has been b). The National Centre for Educational Statistics (NCES), a federal body, looked at how the states’ definitions of “proficiency” at maths and reading compared with its own rigorous one. For grade 4 reading in 2009, not one state held its pupils to as high a standard (see map). Fifteen states labelled a child “proficient” when the NCES would have called her skills “basic”; 35 bestowed that honour on children performing at “below basic” level.

Small wonder parents are crying out for grades that mean something. Helpfully, the National Governors Association and the Council of Chief State School Officers have been pushing for “Common Core” national standards in maths and English. Forty-five states have said they will adopt them. Science standards are being developed by a separate group of 26 states, and were released in April.

The Common Core sets out the essential skills that pupils are expected to learn in every grade. (For example, by the age of eight they should be able to draw a bar graph.) Test results will be interpreted on a single scale, so children in Illinois can be measured against those in Alabama. If faithfully implemented (a big if), the Common Core should make it impossible for states to pretend that pupils are doing well when they are not. It should also make academic records comparable when pupils move from one state to another.

Naturally, this plan has many critics. On the right, some fear the federalisation of schools, which are primarily a local or state responsibility. Some worry that Common Core is a distraction from the more important task of promoting school choice. And some object simply because Barack Obama approves. (His administration is providing $360m to two consortia that are developing tests.) Glenn Beck, an incendiary talk-show host, sees an attempt to indoctrinate the young with “extreme leftist ideology”. He provides no evidence that makes sense.

Complaints from the left are equally varied. Some progressives oppose any kind of testing. Some fret that schools and teachers will be held more accountable for results. And there is a bitter debate about whether requiring students to read more “informational texts” will mean that great literature loses out in the classroom.

In April the Republican National Committee passed a resolution opposing the Common Core. Since then the Republican governors of Indiana and Pennsylvania have agreed to delay its implementation. In Michigan, as The Economist went to press, state legislators hoped to block its implementation for a year.

Michael Petrilli of the Thomas Fordham Institute, a conservative think-tank, supports the Common Core but says he is surprised that it has taken other conservatives so long to mount this fight. However, he says Common Core is likely to prevail. Even if a few states pull out before national tests in two years, probably far more will stay in than supporters had expected.

Most governors from both parties support the Common Core, as do the National Parent Teacher Association, the US Chamber of Commerce and over 70 business leaders. Even the teachers’ unions are making positive noises, though they worry that there will be problems in implementing the new system and that teachers will be blamed. A survey by MetLife, however, finds that teachers warm to the Common Core as they get to know it better.

The most important question, naturally, is whether tougher standards will lead to better results. In rich countries, school systems with exams based on robust national standards (ie, similar to Common Core) perform 16 points better on the PISA test (an international benchmark) than school systems without them, says Andreas Schleicher, an education expert at the OECD, a rich-country think-tank. This puts them half a school year ahead. The effect is larger than almost any other national variable. Of course, people argue about whether this is a causal relationship, adds Mr Schleicher. The debate might be more scholarly if everyone involved had mastered patterns of association in bivariate data—as the Common Core demands of 13-year-olds.