Asalam Alaykum SAIFI, I am pleased to read that you are at school and reading Salah at a young age, I think a lot of people can take note of this and also do the same.
If you are 100% convinced that they are wahabi, then I believe you are right not to pray behind them, instead if you can initiate a jamaat seperately or individually read salah by yourself, this will be better for you.
We the ahle sunnah wal jammah will not compromise our beliefs in Islam and will continue to remain on the haq, despite criticism from misguided groups. You only have to read through the various threads on this site about wahabisim or speak to learnerd ulema on the haq about the fitna the wahabies have created. Furthermore only Allah knows whether someones salah is accepted, these devients (wahabies) have openely disrespected the Holy Prophet (saw), the ahle bait, past righlty guided ulema not to mention their own ulema, propogate the use of suicide bombings, kill innocent people daily. I know I would not read behind them in fear that my Salah may not be accepted. Look at it another way, if someone slapped your dad or mum in the face, would you continue to sit and be friends with them? Disrespecting Hazoor Pak is more than that, and we cannot and will not associate with these devients unless they do taubah and come to the haq.
So it is right for you to raise this question and understand where the land lies, but please do not take this to mean that you can now go and challenge the wahabies to a munazara or debate, furthermore do not get drawn into any acts of violence etc. Remain steadfast on the haq and inshallah come and speak to the rightly guided ulema of the ahle sunnah wal jamaah. Be free to come to Daraloum Qadri Jilania and speak to Syed Mazar Hussain Sha Saab student of Mufakir-E-Islam DR Syed Pir Abdul Qadir Jilani at your earliest convenience for education on deen.