The Advisory Centre for Education, a parents' advice charity, carried out the survey. Spokeswoman Margaret McGowan said parents could not tell whether they were getting all the help they were entitled to from schools and councils.
"Meanwhile, the child is piggy in the middle, not receiving the help they need. This information would help parents decide whether it is realistic to ask for a statutory assessment of their child or whether they need to go back to the school for improved help," she said.
The ACE website survey found:
* Only 10 LEAs list all the required information, with another 25 or so giving some details.
* 22 LEAs have nothing on SEN on their websites. Around half do no more than list all their special schools.
* Sites are often full of "mission speak" or directed at schools rather than parents.
* Some sites are still referring to the old SEN code of practice, replaced more than a year ago, or out of date legislation.