Focus: School tests
A committee of MPs has warned that plans to test pupils more often risks causing greater damage to education.
The damning report by the schools select committee comes as 11 to 14-year-olds across England take their Sats in maths, English and science.
Teachers and opposition politicians called on Schools Secretary Ed Balls to listen to the "groundswell of disapproval" of the testing system.
MPs have warned that the drive to meet Government-set targets has too often become the main goal of education.
"Classroom practices aimed at improving results has distorted the education of some children, which may leave them unprepared for higher education and employment," their report said.
"Substantial evidence" has been given to the select committee that teaching to the test is widespread, MPs said.
An inquiry has been called for to find out the full extent of the problem of schools "teaching to the test".
Members of the select committee want a reduction in the number of times children are externally tested and more use of internal teacher assessment.
The current system of compiling national results from tests taken by every child aged seven, 11 and 14 should be abandoned, the MPs said.
National standards should be monitored by testing a much smaller "sample" of pupils from across the country every year, according to a group of MPs.
They want the exams watchdog to conduct "a full review of assessment standards" as ministers have failed to address concerns over "grade inflation".
The MPs warned the system has become so distorted it is "virtually impossible" to measure national standards.
Schools Secretary Ed Balls has proposed changes to the national testing system, with a pilot project currently under way in more than 400 schools.
Instead of assessing children with Sats at the fixed ages of 11 and 14, the pilot scheme tests pupils when their teachers think they are ready.
Ministers believe that this could encourage schools to help pupils make faster progress.
Teachers' unions have insisted that ministers are isolated in their support for national testing.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said: "The Government should finally accept enough is enough."
John Dunford, from the Association of School and College Leaders, backed the idea of measuring national standards by testing a "sample" of pupils.