You mean it jumps to the left, I think. I don’t want that either, I just wanted the default template on all pages and not the list of child pages.
What worked for me: comment out or delete this section in style.css:
/* =Layouts
----------------------------------------------- */
.layout-sidebar-left .site-main {
margin: 0 0 0 30%;
}
.layout-sidebar-left #secondary {
float: left;
}
.layout-sidebar-left .content-area {
float: right;
margin: 0 0 0 -25%;
}