Hi Youare that's what they do at ds2's school. All 'interventions' are done outside of day-to-day lesson times, effectively disadvantaging SEN pupils with social/communication difficulties further, by making it impossible for them to socialise at lunch/break and at after school clubs. Plus of course it stops them from being able to access support at homework club, which further disadvantages them.
As I understand it, it's the same at all the secondaries in our area, which are now all Academies. It was one of the reasons I didn't want ds1 to attend any of them.
Ds1's school is an indie, as you know, but they refused to let him drop MFL until it became clear that there was absolutely no way he was ever going to even scrape a grade. He did French throughout Y7 and Y8, but was in an support session during Spanish in Y7. The school then tried to dump him and the other boys he'd attended the group with back in the Spanish class at the start of Y8, despite all of them missing the entire first year of the curriculum. When I pointed it out, all they did was get the boys to sit at the back of the Spanish class and do unsupervised 'homework'. I kicked up a stink, but couldn't get them to see what a waste of time that was for kids that needed lots of support and intervention.
Y9 they tried to put them back into Spanish - again, as the French teacher had left and they had been unable to find a replacement, so French was being offered as an optional second MFL during enrichment sessions, which none of them opted to do, effectively leaving them without an MFL to study. This time I wasn't standing for it and the end result is that ds and one other lad now have a supervised homework sessions elsewhere during Spanish lessons and aren't studying an MFL at all, which I am confident is the right decision for him.
From what I've seen at ds' school, it's more about staff deployment than withdrawal of pupils from lessons they need to attend. If not they have no way to explain wasting an entire year's worth of lessons for several pupils that sat and messed about on laptops at the back of an MFL classroom. 
Ds was also withdrawn from Art last year, as they claimed they didn't have another time he could have help with printing his classwork and he was basically refusing to attend anyway, as he really struggles and finds Art humiliating. This year they have insisted he goes back to Art, having missed lots of the techniques the others have been taught and already being disadvantaged by having very poor fine motor skills. 
As you know, we've come close to pulling him out of the school so many times over the past couple of years, but he's actually happy and achieving in the most important areas now, so we're just monitoring closely and keeping everything crossed that nothing changes. That said, they've dropped the ball in other ways a couple of times recently, so I'm not all that confident.