1. Fasting is compulsory, I know, but is it true that there are exemptions for the disabled and schoolchildren?
Fasting becomes obligatory on all Muslims once they reach the age of puberty. However, parents and young people themselves should start practising much earlier. According to one Hadith of the Prophet (s.A.w.) children should start training from the age of ten. Certainly no one should wait beyond the age of fifteen, unless he or she falls into one of the exempt category.
This includes the sick, elderly, menstruating, and travellers. However, with the exception of the chronically ill, all the others mentioned have to make up the missed fasts later. Disability is no excuse for not fasting. People with medical ailments should also fast, unless of course, they need to take frequent medication.
(98 - Siyam 2)
2. At what time does fasting begin and at what time does It end?
The times to begin and end fasting - suhoor and Iftar - are clearly outlined in the Qur'an in Surah al-Baqarah, verse 187. "And eat and drink until the white thread of dawn appear to you distinct from its black thread; then complete your fast until the night appears."
Here in Britain, for some years now, a number of Muslim organisations have been publishing detailed Ramadhan timetables based on data obtained from Greenwich observatory. And it is true that there are variations in some of the times on the timetables. Short of going through the hassle of trying to verify the information personally, the best thing to do is to err on the side of caution, and to begin fasting from the earlier time and open the fast at the later time.
(102 - Siyam 3)