Ideal Indian School is best what i know. It has the option to keep Arabic as Second Language starting from Grade I till Grade X (a period of 10 years). In addition, they have a good standard of islamic studies. They take kids starting from Grade I for prayers and teach them other basics too. My daughter studies at Ideal Indian School in Grade I and i have been having a good experience till now.

Please visit the below link
http://www.idealschoolqatar.com/others.php?id=3