Before the Milan Conference, Deaf people were reading and writing on par with their hearing counterparts. *shrug*
This was in Netherlands...
The empirical data, quite interestingly, do showthat
there is a strong and positive relationship between signing
and reading skills (Chamberlain & Mayberry, 2000;
Hoffmeister, 2000; Mann, 2006; Padden & Ramsey,
2000; Parisot, Dubuisson, Lelievre, Vercaingne-
Menard, & Villeneuve, 2005; Prinz, 2002; Strong &
Prinz, 1997, 2000). For instance, Strong and Prinz
studied the relationship between the signing skills
and the reading skills of a group of 155 deaf children
between 8 and 15 years old. They found a strong correlation
between signing skills and reading skills, even
after age and nonverbal intelligence were partialled
out. In general, deaf children with good signing skills
were also the better readers.
The Relationship Between the Reading and Signing Skills of
Deaf Children in Bilingual Education Programs
520 Journal of Deaf Studies and Deaf Education 13:4 Fall 2008
155 deaf children out of what? 50,000 deaf children? Thanks that sure gonna help me.

What do you mean based on my experience? I wasn't there during the 19 centuries ago. I'm talking about from 19 century ago and now, nothing had proven me that one approach is more effective for the majority of deaf.
I'm not even going to considered 19th century as an example. Disability-related issues were much less understood than now and anybody with disability was considered invalid and useless. Their approach was like trying to teach a handicapped man to walk and blind man to see. They were using wrong approach and wrong tools.... due to misconceptions, misunderstanding, and taboo.