@Life_is@no-pony.farm @MissConstrue@mefi.social @ariaflame@masto.ai Sorry, but Ramadan's breakfast (Suhoor) can be a perfectly normal cereal breakfast. There is no nutritional reason why following Ramadan causes lower concentration, and I am not even a Muslim. And from what I understand, breakfast is the only meal that really matters for school results, especially in Germany where school usually ends at lunchtime.
However lots of Muslims, just like most of members of other religions, totally neglect their religion except during special holidays - such as Ramadan. All the extra religious stuff they are doing, e.g. studying the Quran, extra prayers, and also the extra visits from/to extended family can overwhelm those not used to them, and can easily cause the described concentration loss.
You would get similar results for Christians, except not, as Christian holidays are already recognized in the school calendars.
The solution to this is not having fewer Muslims, but having fewer hypocrites of any faith. It is okay to be honest to yourself and to believe in nothing.
Definitely don't raise children like I was raised Catholic - once firmed, rarely ever going to church except on Ash Wednesday and Day of Prayer and Repentance. I was not actually Catholic except on paper. Either one is a believer, or one is not. That is both fine. But let's not do the thing where we go through the motions with nothing behind it. As that indeed can be quite harmful.