913 for Woodlands Circle to Woodlands Interchange
168 for Woodlands Interchange to Tampines OR
969 for Woodlands Interchange to Tampines Interchange
I can't specifically tell which would be most convenient for
you; neither did you specify the school you have to go to. But here
are some info on the two services that you can take to
Tampines:
168: To Tampines, it should take about 35 - 45 mins to arrive.
However, if you wish to go to Tampines Interchange, you will have
to (a) alight at the bus stop opposite Tampines Regional
Library. cross the road and transfer to another service to
reach Tampines Interchange (1 stop), (b) alight at the Blk 242,
Tampines Ave 4 bus stop and walk past Tampines MRT into Tampines
Interchange, or (c) alight at the bus stop opposite Century Square
and transfer to Service 3 (2 stops).
969: No idea of how long it takes to Tampines, but the service
will have to pass through Yishun before it hits the expressway;
therefore, it may probably take longer to reach Tampines if you're
directly using this service to reach Tampines. Furthermore, there
will be no stops from the last stop in Yishun all the way
to Tampines; the bus will just go straight to Tampines
Interchange once it leaves the TPE.
So it's your choice, you decide...