I'm alright with this. There was an article several years back (http://www.theglobeandmail.com/news/toronto/toronto-district-school-board-defends-hosting-muslim-prayer-sessions/article585899/) about how Muslim students may end up missing class time because they were leaving on Friday's to attend prayer. It sounds like  the current arrangement ensures they do not miss class. Also, the only reason they're main day of worship conflicts with class is because the school boards were originally Christian, so Sunday was the day of rest and Saturday the prep day.

Further to some of the critiques I've read in the comments:
1)Why this but no Lord's Prayer  
The Lord's prayer was removed because all students were required to hear it at the beginning of the day. Thus all students were forced to participate. This is optional , and does not occur during class time. 
2)Choose religion or school
I find this divide more likely to encourage private religious schooling which would decrease integration.