Questions about cost and location.

Oh dear, why did you choose BIS? Scandinavian school yes but BIS?

Where is work?

Are you paying your own rent, as 3000 will not cover living costs and rent in Waterloo?

Are you on a Belgian contract so you can claim your 300 a month in child benefit and possibly non working spouse tax allowance as well as 2 dependent children allowance?

What languages do you speak?

Well yes it's safe to go to school by bike if you can afford a house close enough to school.

I spend 200 euro a week on food for 2 adults and 4 children.

Public transportation is a standard cost throughout Wallonia wither one bus company called TEC, plus trains run by SNCB. Where do you want to travel to? You can get season tickets just for TEC, or combined with de Lijn if you travel into Flanders, or combined with STIB if you travel into Brussels or combined with SNCB if you use the train. A normal yearly season ticket for 12-24 years is €155 and for a 24-64 is €375, that's TEC only buses.
http://www.infotec.be/index.aspx?PageId … 5930483492

You can see a Waterloo bus map on this link. SSB and BIS are in the domain a bit futher into the woods than Berlaymont school, an excellent local schools. The 121 to 129 TEC buses could be used by SSB and BIS children to get to school too.
http://www.infotec.be/Files/TECBW/NetPl … Braine.pdf