Phillipson favours an approach of earlier intervention, something that is welcomed by campaigners and MPs.
Schools Minister Georgia Gould, who recently inherited the SEND brief, has been visiting constituencies on a "listening" tour exercise.
A Department for Education spokesperson said the government inherited a SEND system "on its knees".
"We're determined to put that right by improving mainstream inclusion so every child can thrive at their local school," they said.
"We've held over 100 listening sessions with families and will continue engaging parents as we deliver reform through the Schools White Paper."
Phillipson has had praise from MPs for being accessible and ready to hear their thoughts, and they point to this as evidence that Downing Street has learned lessons from the summer, when numerous Labour MPs rebelled against the government's proposed cuts to welfare.
Ministers favour setting up more specialist provision in mainstream schools, but MPs have warned that there cannot be a half-hearted approach to giving schools and councils what they need.
"If SEND reform is about saving dough rather than improving the system then it's not headed in the right direction," said Labour MP Neil Duncan-Jordan.
Labour MP Rachael Maskell said that if the upcoming budget does not show that the government is adequately equipping schools and councils - such as increased workforce funding for roles such as speech therapists, health visitors and physiotherapists - then she will not be supporting reforms.