"even under section 28 homosexuality could be discussed questions asked and answered. "
Unfortunately, this is not true. What would and would not count as "promotion" of homosexuality was left utterly unclear in Sec28, with the result that teachers were left standing in a minefield with no clue where the mines were. The result has been very well documented - teachers simply chose not to talk about homosexuality, or about sexual health for homosexuals - and the results were disastrous. Ask any LGBT person who experienced school while S28 was still in force, and they will tell you the same thing - their teachers were overwhelmingly silent on the issue.
Likewise, these schools have not made clear what "promotion" would be. Is it "promotion" to point out that gay couples can live just as happily as heterosexual couples? Is it "promotion" to point out that there is no evidence whatsoever that gay couples make worse parents? In a "neutral discussion" about homosexuality, is it "promotion" to even talk about the arguments in favour of accepting gay people for who they are? All of these things could easily be construed as "promotion", and teachers who say them could run the risk of being sued or fired.
There is no such thing as "promotion" of homosexuality. You might have a case for this if teachers were deliberately telling children to adopt a homosexual lifestyle even if they didn't want to, but there is not a shred of evidence to show that this is happening. Instead, people who have a problem with homosexuality use the language of "promotion" to stifle education about it, just as they did 25 years ago.