After nearly a decade in which traditionalists and teachers have fought fiercely about whether rising exam grades meant higher standards or easier exams, Mrs Shephard said that there was no evidence of falling standards.
Despite an authoritative report which found that standards had not changed, she announced measures which aim to make GCSE and A-level tougher.
There will be more emphasis on grammar in GCSE English and a separate English Language GCSE. At both GCSE and A-level, the use of calculators will be restricted and the use of open books in English exams will be reviewed.
At A-level, more pre-19th century literature will be compulsory. At present candidates must study Shakespeare and one other pre-19th century author out of eight texts. The new requirement will be for four.
The report from the School Curriculum and Assessment Authority, the Government's exam advisers, and the Office for Standards in Education says that there is a shortage of evidence about the issue of standards because not enough past scripts are available.
Mrs Shephard said: "Today's report shows no hard evidence that standards are falling but we have been looking at the past. It is the future that is important."
The 50 independent examiners who drew up the report on English, maths and chemistry at GCSE and A-level found that candidates have to cover more topics than 20 years ago. In maths, the only subject in which there was evidence of a slight fall in standards, there was less emphasis on topics such as reasoning and problem-solving.
Chris Woodhead, Chief Inspector of Schools, told BBC Radio 4's Today programme: "The report is saying to the Government that the danger is that more and more students are being educated for longer and longer at greater public expense to know less and less."
Mrs Shephard said she had been appalled by the lack of evidence from exam boards for the study. She called for a national archive of evidence about exam standards.
The most worrying feature of the report was evidence of inconsistencies between syllabuses and exam boards. She wanted the four English exam boards and three vocational bodies reduced in number but she added: "I am not in favour of denying schools and colleges choice and innovation by nationalising all examination provision under a single board."
However, David Blunkett, Labour's education spokesman, said he was prepared to consider a single board for England and single boards for Wales and Scotland.
Leading article, page 21
Hardy perennial: But are the questions harder?
A-level English 1956
The Mayor of Casterbridge
a. To what extent do the seeds of Michael Henchard's downfall lie within his own character?
b.Write an acccount of the life of Lucetta and show how, in their reactions to her, other people in the story reveal their own characters
A-level English 1991
Thomas Hardy: Jude the Obscure
What can you find in the opening chapter which prepares you for what is to follow?
``Jude the Obscure - a study of failures.'' Do you agree?